Could it be warping related? As in the ones that usually happens by lifting corners.

Another candidate or a partial subject is an uneven print bed. It does happend over time. If your printer has a layer test print you could check if the print result is even.

Anyway, both of the above can be alleviated with a slower print speed to give the extra time for print bed adhesion. Not really a guaranteed fix, but the results might be good enough.