820-00840 requires SMC reset to turn on

After shutting down and closing lid, A1408 won't turn back on without first doing an SMC reset.
Shutting down without closing lid, machine turns back on without SMC reset.
No damage or liquid traces around hall sensor or SMC.
When testing with trackpad cable unplugged (LID_OPEN disconnected), unit turns on fine and issue does not occur.

I have not diagnosed a hall sensor issue before and am not sure how to proceed with testing whilst being able to test with lid open/closed.
Can a magnet be used to test values out of chassis? I am not sure how to proceed.

NOTE: Liquid damage around CD3215 resistors was repaired but issue pre-dated this charging fault.

Thank you in advance

Hall sensors may work if no problem disconnecting trackpad.
Something bad with trackpad, which affects LID_OPEN signal probably.
Check LID_OPEN level with lid open/close.

Just in case, check HALL_SENSOR_LEFT/RIGHT signals too.
You can use magnets approached to the sensors.

Very strange. The issue is no longer present.
Even after an upgrade from High Sierra to Monteray, the issue had persisted.
Once booted without trackpad and 3.5mm board connected (which I believe houses the other sensor), SMC reset was performed, connectors brushed off and reconnected and it now works. I should mention that I had previously disconnected and inspected the connectors but did not brush them off (they looked great and were clean) nor perform an SMC reset in between reconnecting them.
I am not complaining, I just wish I knew what did it...

Thank you very much for getting back to me with help.
Should I delete the thread or leave it as strange as the "solution" may be?

No need to delete the thread...