Usually only one axis skips steps, especially since the MK4 has collision detection. A shift in both axes would rather indicate a steel sheet shift imo

Fantastic! Glad you got it in the end

Did you losen the idler tension screws? TPE requires that the tension is very very light otherwise it tends to buckle around the gear before entering the nozzle tube. Reducing retractions to a minimum is also always a good idea, as well as limiting the max flow rate.