Hi,
I've been running into the same problem with a lithoplane.
The prints starts with the diagonal. Working up and to the left, the printing continues smoothly and evenly, but when the second half needs printing (from the diagonal down to the right), the printing is very rough and occasionally manual intervention is necessary to stop the layer (last line, but the problem grows exponentially from there) from peeling off.
The bed levelling has been checked and should not be an issue.