Just to add my +1, I also encountered this error (twice):
couatl v4.0 (build 4642)
panic log started on Wed Apr 6 15:00:18 2022
problem raised by addon <unknown>
Traceback (most recent call last):
File ".\common\fsm.py", line 67, in switchToState
File ".\GSX\assistanceServices\baggageLoader.py", line 265, in enter
AttributeError: 'CargoLoader' object has no attribute 'extension'
{'Airport': 'YMML', 'Requested assistance services at': 'Parking 2', 'User Pos': (-37.67814833098507, 144.84791601771414, 136.461 m, 4.18008 m, 170.70440852776412, 0.013134235516190529, 0.008115781471133232, -0.0, 3.98068812789917, 1.0)}
Aircraft used: PMDG 77F, no custom aircraft profile.
Airport: ORBX Melbourne with the GSX profile provided by ORBX.
Sim: P3Dv4.4
OS: Windows 11
After arriving at my Gate (not preselected), I opened GSX via Ctrl+F12 and selected "Request Deboarding".
The previous boarding at departure had no issues. Restarting couatl and then again requesting deboarding works fine.
I already did a Live Update after first seeing this error last night, I still received this error again today.
Cheers,
Eric