UM3 Extrudes during Active Leveling

[donbon 0]

During the Active leveling phase of the print, a few CM of filament is extruded and sticks to the nozzle like a plastic booger. So when the Bed touches the nozzle for active leveling two things happen:

1. It causes incorrect bed leveling due to the extra material between the nozzle and the bed

2. The nozzle clogs a bit, such that it does not extrude properly at the start of the print (The purge phase helps this a bit, but not always)

This started a week ago after I've been printing with TPU quite a bit. Any suggestions? 

[donbon 0]

I've figured it out: The issue was that my the TPU had absorbed too much moisture. I think what's happenig is that the moisture in the filament vaporizes in the print head, and the resulting increase in pressure causes some of the filament to be extruded prematurely. I fixed the issue by running the TPU through a filament drier.