I have set up a number of eTAP SRAM rear Derailleurs and never had an issue. I set up a 44 tooth XPLR cassette with the XPLR Rival eTAP rear Derailleur. I got the chain sized, on the pulleys and everything looked fine. For doing the micro-adjustment it was difficult to do it with the chain on (you have to align the pulley with the 2nd to largest COG). The alignment never worked right and I found that I could shift all the way to the largest COG and all the way down to the smallest - but the shifting would stop half way up the COGs and never got to the top.
I could see the shifts signaled to the Derailleur by the flashing of the indicator light when I hit the shifters up or down.
Every now and then the shift would go all the way to the largest COG but this is only after I seriously mess with the mirco-adjustment whereby it moves a whole shift up or down.
The Derailleur is brand new and the issue started right at the install - didn't put any miles on the bike.