Your theory was absolutely correct — the slight nozzle movement during leveling checks was indeed the root cause of my problem. While troubleshooting, I also tried the suggestion of putting a piece of paper under the nozzle during leveling, which worked great and helped oid those nasty first layers. Thank you for sharing that tip — it sed me a lot of frustration.
At first, I checked my hotend and everything seemed tight, but I decided to buy a new one just to be sure. While installing it, I noticed that the two screws marked as 3 and 4 in the image (attached) would not tighten properly. Even after replacing the entire extruder unit, these screws still wouldn’t tighten up, and the issue persisted.
Eventually, I replaced these two screws with slightly larger screws, which then tightened up perfectly. After this change, my printer is now running flawlessly and producing first layers like new.
I would strongly recommend everyone to check these screws regularly (perhaps once a month) as part of routine maintenance — it can prevent many headaches and ensure consistent print quality.
Thanks again for helping me (and surely many others) identify and resolve this issue!
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