I use my hardened nozzle all the time with a variety of filaments, mostly PLA and Edge with a few of ColorFab XT CF20 and since fitting the socks printing has improved immensely but yesterday I had a problem. The problem manifested itself on the first layer as strange flattened blobs appearing as the track was laid. Looking at the nozzle assembly it appeared that the tip was not poking out of the sock and pushing it on harder made no difference. I took off the sock and inside there was some deposit around the nozzle recess that I removed and refitted the sock but still no real protrusion through it. Next, I looked at the nozzle and on close inspection I could see there was some build up of deposits, so I heated and wiped but the deposits did not come off and were rock hard. Careful use of a sharp pointed model knife eventually removed all of the deposit and the sock was refitted . . . success, the tip of the nozzle protruded and the next print performed well. So, long-term use with socks can cause a build up of deposits on the nozzle under the sock, pushing the sock down so that the sock touches the work-piece; most likely due to a wicking process between the nozzle and the sock. Therefore, a regular clean of the nozzle and sock is recommended.