Plate uniformity

Ever since we had our M2 reader repaired for a motor issue is has given variable absorbance readings across the plate. The bottom row of the plate gives readings ~2x higher than seen in our other plate readers and this increases as one moves up the plate so that the top row gives readings ~8-fold higher than we get in our other readings. Any thoughts on what would cause this, and how it might have happened during the recent repair? Or are the two unrelated and just happened at gthe same time?

thanks, Mike