since all the issues are on the corners I'd say its a belt problem causing there to be play in the print head during movement transitions. Could be the filament also. Do you live in a humid environment? If its the same roll that worked and now doesn't it may have absorbed moisture. if its a new roll or different brand it could just be a bad roll.

Snapmaker U1 is awesome. Highly recommend especially if you want to print multi-colour. I can't go back to a AMS now. I posted a video recently on a project using it. Handles TPU with no issues also

I've done well on etsy selling laser SVG files, but not as good with 3D prints, haven't found the right product or niche for them yet. Physical objects are so much more work when you have digital files selling and you don't need to worry about shipping :)