I have had my nozzle plug up and the only way to clean it is by fully disassembling it and using a small drill bit. I never have a problem going from PLA and switching to ABS. It is the ABS to PLA direction that is dangerous for me. For some reason, it seems a little bit of ABS plastic stays in the nozzle and eventually it comes loose and plugs the nozzle at lower temperature. Some times I can turn the heat up and get it out. But always the print is destroyed.