Extruder catching/dragging printed filament  

Extruder catching/dragging printed filament

I built my MK2S from the kit, and was able to successfully make some demo prints from the card (the whistle and triceratops skull turned out great).

Then I sliced/exported a 3D printing model I found online, but the printer kept snagging the material, and it got melted to the outside of the extruder. I've done my best to clean it all off (heating it up and using tweezers, wet/dry/alcohol-soaked paper towels) but now even the Prusa logo won't successfully print.

I recalibrated it and the calibration seems to have worked successfully (got the "Good Job" message) though I did have to adjust the PINDA probe a few times to do so. The zig-zag calibration print works most of the time, but even that one isn't reliable, one of the corners often winds up curved instead of straight, like it's being pulled along after being printed. When I tried printing the Prusa logo, the first layer looked alright but I wound up with a mess of plastic around the extruder tip.

I'm not sure if I need to increase or decrease my Live Z adjustment, or if there's some other problem that could be causing this. I just got this a week ago and really hope I don't need replacement parts this early on, especially since I was hoping to 3D-print part of a Christmas gift.

Tonight when I'm back home I'll record a video of one of the failures, hopefully that'll help people steer me in the right direction.