Tested the autoreverse board yesterday: works perfectly, install was ridiculously easy. No failures, no errors.
I did not need to fine-tune the detection circuit with a jumper wire. So far, so good.
There is a small spark when the loco bridges the gap between track sections. Not big enough to be of concern.
The loco does not hesitate or notice the phase reversal, nor does the sound. I tested it around 30 times over two days. Four power on/off cycles.
I will put in an order for a second board. Even though I don't need it for the upper reverse loop now, I want to have it on hand. No idea about the future availability of the board, so just being cautious.