Great post! I also recently assembled my UM1 and came here to find answers after melting my PEEK. I had sarted my first print (ultimaker man !) But I stopped after a short while when I noticed th print sliding sideways. Fixed a loose pulley.but left the temp at 210 or 220 for some time. Extruder quit working so I read about setting temp to 250 to clear a clogged nozzle. Fooled around reading wiki while nozzle was at temp and when I glanced again the nozzle was discolored and spewing burnt plastic droplets and some smoke. After cooling... PEEK plugged. Dismantled and hole through it plugged with material. Drilled out from nozzle side but now when reassembled filament jams at entrance to brass tube because its now off centr. I though of using 10 mm spacers at bottom of wood to elieve tension then recalibrate z stop till I get parts from NL. I did notice the blue LED intermittently flashing and I did have a MINTEMP error whichI thought I fixed so I'll include a pic of my strain relief too...
