Hello,
something must have changed when you are getting different results now.
Have you changed your equipment and/or anything in your workflows?
In which software do you clean up your models? And is it still the same version as before the issues had started to occur?
The preview quality does not have to be the problem, it depends what settings did you use for the preview quality, I can see you have changed the number a bit unreasonably: https://support.capturingreality.com/hc/en-us/community/posts/115001357172-High-model-normal-model