Core One kit Extruder stuck after successful test prints  

Core One kit Extruder stuck after successful test prints

Greetings and hello, first post,

my Core One kit printed successfully (Keychain testprint and a few grams more), now it got stuck. Badly, I couldn't get the filament out by other means than dissassembly (I have the tool for the extruder, no concerns about rebuilding. But this seems out of the ordinary).

Filament came with the printer (PLA orange), unboxed only yesterday.

Question is, what happened? Why did the filament get stuck, how do I fix this for the future?

Theories so far: 

• Hotend not properly inserted / tightened (will pay attention)
• Thermistor defect (one possible explanation I found)? It shows 93 kOhms for the hotend, 94 kOhms for the CNC block. Readings in the "Footer" while heating / cooling look sane. The latter one's grub screw was tightened very lightly during assembly, definitely not crushed.
• Idler pressure (from 3D printing handbook, "Troubleshooting"): The screw tips are slightly recessed, screws are 30 mm (not e.g. 25) and visually it's similar to the assembly manual. It does feel very "crunchy" though when moving, as the screws' threads rub against the CNC part. Both idler bearings move freely. I'll reduce spring tension a bit for the next attempt.

That said, I have zero hands-on experience with 3D printing. Any input is appreciated.