Sorry to hear that you’re experiencing this issue! If you’d like to write to us at support (at) zyyx3dprinter.com, we’ll be happy to offer advice on printing fine details.
We’re glad that you’ve otherwise had a positive experience, though!
YOu dont say what software your slicer is. But Simplify3d has an horizontal offset feature that will allow you to adjust tolerances on a part that fits into another part. Your software may have the same issue.
It is a common problem, particularly when the person who designed the model did not take into account the tolerances that are needed for die swell, vibration, shrinkage, etc.
As for PLA, I swear by Sainsmart. The filament is always in spec, and reliably prints different colors with the same settings for all.