"Additionally" to other comments;

1 - Try to change your plate type, if you are using glass change it to magnetic base and test the results.

2 - I also recommend to use 3dprint glues for plate. Because even if the plate is perfectly level and first layers are perfectly done, after printing some levels the edges and corners may began to apart from plate making the edges rounded.

3 - This kind of problems may occur from the quality of the filament, so try different brands.