Massive Layer shift after 2 hours

Starting last week I've started having significant issues with the X axis of T0 on my V-Core 4 500mm IDEX printer.

I'm getting a huge layer shift and it's very clear that the toolhead is no longer properly homed after a couple of hours mid-print. After cancelling the print, and it going to the park location, it's no longer on the ooze guard.

I heard a grinding sound coming from the carriage rail bearing for T0 several days ago. I disassembled the toolhead to see if there was something in there. I've cleaned the rail, and it seems to move ok, but I'm still concerned that there's a bearing issue. Could that be responsible here?

Otherwise I'm at a loss. Suggestions welcome.