Anyone seen something like this?

[dreko]

Running multi layered PDF files on top of each other. Files would print a layer, return print to starting point for additional print layers. Registration and alignment were excellent.
Then it started printing additional layers slightly out of registration.

Nozzle check is perfect
Media gap is perfect
Calibration is perfect

I am printing on a cotton coated fine art paper (roll)
Any idea why the printer is shifting additional print layers off to 1 side?

thanks