When the encoder is near the edge of a pulse you’ll get flickering of the pulse signal.
One issue is that the pulses are counted and not reset. A few lines of code could decrease the count by 1 every so many cycles and that would probably take care of that.
A bigger issue is that the Teensy has no way of knowing if its a stationary flicker or rapid steering wheel movement. I don’t know the best way of dealing with that, other than reading the full quadrature (2 wire connections) so that the Teensy knows steering wheel direction (then you could do fun things like steer assist with a steer valve too). That’s what the OEM systems do - read the full quadrature.
Another issue is that the digital pin is read once per cycle and that read frequency is lower than the pulse frequency during steering. That causes aliasing of the signal - missed pulses. You’d pretty much have to re-write the firmware to use interrupt service routines to track the steering wheel position to fix that one. That’s really messy when its an all in one board and the same pins could be used for a pressure switch or an analog sensor and the same “stop-steering” function can be triggered by over current.
When there are so many different possible combinations of things its hard for the firmware guys to write firmware - they can’t test every possible combination of AIO connection.
The easiest thing to do is to set the pulse count in AOG pretty high. I think I have it set to 14 in my 8300 and that seems to work without any modifications. Like you, I also just piggy-backed one of the Deere encoder signal wires.