If it’s not the TRX, then it’s either the ANC or the SUM board.
If it’s not them, then it’s the BTS cabinet itself 🙂 It’s extremely rare though…
Try placing the TRX board into another slot of the cabinet ?
And finally, try re-creating the cell / BTS from scratch in the OMC-R.
You’re right, an ABIS issue would impact all TRX in the cabinet. Only an Abis misconfiguration could explain this… but is it possible to misconfigure the Abis ? Perhaps a VSAT ?