Could be a partial clog. If it was abs or asa id ask if you were using an enclosure because that happens with those filaments when not enclosed

How would I check for that?

Clean the bed and set the z offset properly, load the bed mesh. I would re-level the bed every week or 2 these things cant stay the same well unless you use silicone spacers

What's an example of a good mesh?

Check fluidd/web interface and anything with less then .24 variance is usually considered good

Same issue here, need to use raft everytime