Unanswered PETG clear, brown (burned?) spots

After a successful print, I tried again. At end of that print I found it about 7/8 good, then a mess. It was loose on the bed which I thought at first was the issue.

There are, on the first failed layer, a couple of dark spots (burned?). I now wonder if something else is at work here and the print dislodged from the bed because ti became fused for a moment to the object.

This is some old MakerGeeks PETG that has been in unknown environments for some time.

 

I tried PLA and it broke free of the base as well, but did not burn. Ended up adding a raft and it printed fine.

Went back to PETG and it also completed, but, was a bit stringy and had a rougher appearance at the start end end of the print, where the part is thinner and narrower. I thought I had bookmarked a nice little run down on PETG issues like that, but will have to hunt it up again.

 

I've never had PETG stick the nozzle to the print but I have seen the nozzle push against a clump too large to remove which messes with the alignment. Only seen that on long flat sections where I purposefully overextruded the filament to get the first layer right.