I have only had one hiccup with mine.... but let me be extremely clear about it.. I WAS TRYING TO MAKE IT MESS UP... this is not a DP issue. I do this with all my markers to learn their ticks..... turns out, if you grossly overlube the bolt, it will stick. But DUH! De-pressurized the marker completely and wiped off the bolt, re-lubed it like its supposed to be done, and she works perfectly again. HAHAHA.