I can confirm that it is standard Tascam AES/EBU pin out. I have seen the behavior you are describing, but could not reproduce it. I did have all 8 channels in both directions working at one point.

However, I now have a problem where I can see input on all 8 AES channels in the meters, but those signals do not reach the FX chains or algorithms they are connected to. Changing the clock (internal, AES, or Dante) did not help that problem. I’ve given up on AES for now since I have Dante and MADI. Those seem to work everytime.