I recently printed several runs of calibration blocks after doing some work on my Form 2.
I noticed features start to get less crisp, and more bleed around the bottom of my direct-on-base part. Initially I thought it was because of the changes I was making. However a cleaning of the optics (glass, mirror, galvos) fixed that right up.
Interestingly, I had just done a less thorough cleaning (glass, mirror) not long before running #2. Things went from OK to marginal pretty quick between #2 and #6. After the last cleaning all my prints are coming out perfect.
Sharing this for others to see an example of how dirty optics can manifest.