I did not notice anything unusual.
OK, I will look into trying that, but I believe the AX-12A outputs 5V responses while the Raspberry Pi can only accept 3.3V. Looking at the thread you linked, I guess I would need a level shifter?
It also occurs to me that we have oscilloscopes and I could try inspect what’s being sent or maybe try to simulate sending commands with a signal generator, but I’m not very familiar with the EE equipment.