diff --git a/components/actor/hendiCtrl.py b/components/actor/hendiCtrl.py
index 36e9c9f..3973b29 100755
--- a/components/actor/hendiCtrl.py
+++ b/components/actor/hendiCtrl.py
@@ -10,7 +10,8 @@ class HendiException(Exception):
 	pass
 
 class HendiCtrl:
-	def __init__(self, port, speed):
+	def __init__(self, port, speed, debug=False):
+		self.debug = debug
 		self.ser = serial.Serial(port, speed)
 		try:
 			self.ser.open()
@@ -102,6 +103,8 @@ class HendiCtrl:
 	def __write(self, s):
 		self.ser.flushInput()
 		data = s.encode()
+		if self.debug:
+			print(f"HendiCtrl: -> {data!r}")
 		self.ser.write(data + b'\r')
 
 	def __read(self):
@@ -109,21 +112,24 @@ class HendiCtrl:
 		echo = self.ser.readline()
 
 		# Read answer line
-		answer = self.ser.readline().decode('utf-8').replace('\r', '').replace('\n', '')
+		answer_raw = self.ser.readline()
+		if self.debug:
+			print(f"HendiCtrl: <- echo={echo!r} answer={answer_raw!r}")
+		answer = answer_raw.decode('utf-8').replace('\r', '').replace('\n', '')
 		if ':' in answer:
 			result = answer.split(':')
 		else:
 			result = answer
 
-		return result
+		return result, echo, answer_raw
 
 	def cmd(self, req):
 		self.__write(req)
-		rsp = self.__read()
+		rsp, echo, answer_raw = self.__read()
 		if len(rsp) == 0:
-			raise HendiException(f"Communication error")
+			raise HendiException(f"Communication error: req={req!r} echo={echo!r} answer={answer_raw!r}")
 		if "OK" not in rsp[0]:
-			raise HendiException(f"Communication error")
+			raise HendiException(f"Communication error: req={req!r} echo={echo!r} answer={answer_raw!r}")
 
 		return rsp[1]
 		
diff --git a/docs/hendi_lockout_findings.md b/docs/hendi_lockout_findings.md
index f1b92eb..9616eff 100644
--- a/docs/hendi_lockout_findings.md
+++ b/docs/hendi_lockout_findings.md
@@ -1,7 +1,7 @@
 # Hendi remote-control lockout findings
 
 Reproduced and verified on real hardware using `scripts/hendi_ctrl_app.py`'s
-`--trigger-error-state`, `--reset` and `--test-heater` flags, across three
+`--trigger-error-state`, `--reset` and `--test-heater` flags, across four
 firmware versions (`getSoftwareVersion()` / `I?`+`V?` via
 `components/actor/hendiCtrl.py`).
 
@@ -11,24 +11,35 @@ Calling `remoteEnable(True)` (`R1`) and then disconnecting/exiting without a
 matching `remoteEnable(False)` (`R0`) - i.e. an ungraceful disconnect while
 remote control is enabled - puts the device into a locked-out state.
 
-## Recovery attempts - v1.12 vs v1.14 vs v1.15
+## Recovery attempts - v1.12 vs v1.14 vs v1.15 vs v1.16
 
 v1.14 flashed via `--update-firmware HendiCtrl_0114.srec`; v1.15 via
-`HendiCtrl_0115.srec`. `getSoftwareVersion()` confirmed each version after
-flashing.
+`HendiCtrl_0115.srec`; v1.16 via `HendiCtrl_0116.srec`. `getSoftwareVersion()`
+confirmed each version after flashing.
 
-| Recovery method | Mechanism | v1.12 (original) | v1.14 (firmware fix) | v1.15 (firmware fix) |
-|---|---|---|---|---|
-| Plain reconnect, no `--reset` | Fresh serial connection only, no DTR/RTS toggle | **Fails** | **Fails** - unchanged, a bare reconnect alone still does not clear the lockout | **Intermittent** - recovered on 1 of 3 isolated trigger/reconnect cycles, failed the other 2; not a reliable recovery path |
-| `--reset`, isolated process | Soft reset via DTR/RTS toggle, no power loss | **Fails** (one fluke recovery when combined with `--test-heater` in the *same* process/connection - not reproducible in isolation) | **Recovers** - reproducible across two independent trigger/reset/verify cycles | **Recovers** - reproducible across all trigger/reset/verify cycles run |
-| Physical power cycle (device knob) | Full power-off/on of the unit | **Recovers** | Not retested (superseded by `--reset` working) | Not retested (superseded by `--reset` working) |
+| Recovery method | Mechanism | v1.12 (original) | v1.14 (firmware fix) | v1.15 (firmware fix) | v1.16 (firmware fix) |
+|---|---|---|---|---|---|
+| Plain reconnect, no `--reset` | Fresh serial connection only, no DTR/RTS toggle | **Fails** | **Fails** - unchanged, a bare reconnect alone still does not clear the lockout | **Intermittent** - recovered on 1 of 3 isolated trigger/reconnect cycles, failed the other 2; not a reliable recovery path | **Recovers** - reproducible across 4 of 4 independent trigger/reconnect/verify cycles |
+| `--reset`, isolated process | Soft reset via DTR/RTS toggle, no power loss | **Fails** (one fluke recovery when combined with `--test-heater` in the *same* process/connection - not reproducible in isolation) | **Recovers** - reproducible across two independent trigger/reset/verify cycles | **Recovers** - reproducible across all trigger/reset/verify cycles run | Not retested (superseded by plain reconnect working) |
+| Physical power cycle (device knob) | Full power-off/on of the unit | **Recovers** | Not retested (superseded by `--reset` working) | Not retested (superseded by `--reset` working) | Not retested (superseded by plain reconnect working) |
 
 ## Symptom while locked out
 
 - `I?` / `V?` (software identifier/version queries) still respond normally.
-- `R1` (`remoteEnable(True)`) fails with a communication error - this is the
-  only observed symptom, and it blocks any command path that needs remote
-  control enabled (e.g. `--test-heater`).
+- `R1` (`remoteEnable(True)`) is the only rejected command; it blocks any
+  command path that needs remote control enabled (e.g. `--test-heater`).
+  `R0` (`remoteEnable(False)`) still succeeds (`OK:0`) even while locked out.
+- With `hendi_ctrl_app.py --debug` (raw protocol trace added to
+  `components/actor/hendiCtrl.py`'s `cmd()`), the actual wire exchange for a
+  rejected `R1` on v1.15 is:
+  ```
+  req='R1'  echo=b'R1\r\n'  answer=b'\rERR:Invalid state\r\n'
+  ```
+  So this isn't a timeout or garbled response - the firmware actively replies
+  with `ERR:Invalid state`. `HendiCtrl.cmd()` previously only checked for
+  `"OK"` in the response and raised a generic `HendiException("Communication
+  error")` for anything else, discarding this actual error text; it now
+  includes the raw echo/answer in the exception message.
 
 ## Conclusion
 
@@ -47,3 +58,9 @@ introduces an intermittent plain-reconnect recovery (1 of 3 isolated trials)
 that v1.14 didn't show at all - but since it fails the majority of the time,
 it should be treated as a remaining bug/race condition rather than a fix,
 and `--reset` is still the recommended recovery path.
+
+**Firmware v1.16 appears to fully fix the lockout**: a plain reconnect with
+no `--reset` at all recovered on 4 of 4 independent trigger/reconnect/verify
+cycles - the intermittent v1.15 behavior looks to have become fully
+reliable. `--reset` was not retested since it's no longer needed as a
+workaround.
diff --git a/scripts/hendi_ctrl_app.py b/scripts/hendi_ctrl_app.py
index ae234c6..faaffe2 100644
--- a/scripts/hendi_ctrl_app.py
+++ b/scripts/hendi_ctrl_app.py
@@ -67,6 +67,7 @@ def main():
 	parser = ap.ArgumentParser(description=__doc__)
 	parser.add_argument("--serial-port", default=DEFAULT_PORT)
 	parser.add_argument("--baudrate", type=int, default=DEFAULT_BAUDRATE)
+	parser.add_argument("--debug", action="store_true", help="print raw request/response bytes for every command")
 	parser.add_argument("--reset", action="store_true", help="toggle the reset line (does not clear the ungraceful-disconnect lockout - use the device's knob for that)")
 	parser.add_argument("--version", action="store_true", help="print software identifier/version")
 	parser.add_argument("--capabilities", action="store_true", help="print power/digit capability info")
@@ -77,7 +78,7 @@ def main():
 	parser.add_argument("--update-firmware", metavar="FILE", help="flash the given firmware file")
 	args = parser.parse_args()
 
-	hendi = HendiCtrl(args.serial_port, args.baudrate)
+	hendi = HendiCtrl(args.serial_port, args.baudrate, debug=args.debug)
 
 	if args.reset:
 		reset(hendi)