The crazy thing is that I have experienced this while using PLA, it is like the PLA was spliced using ABS.
An every so often the spliced area would try to go though the extruder but cannot quite make it because the hot-end is at PLA temperatures and clogs.

To remove this clog I simply increase the temperature to ABS levels and with a firm grip on the filament push it through until the ABS splice in completely though.
After which I can again print normally again until this crazy, what is believed to be an splice made from lets say is a different type of filament clears the nozzle.

Can I help you! I can clear my own though still do not know exactly why this happens to me.
I guess I am saying sometimes we have to come up with our own solutions. An on this occasion it appear that is exactly what we have done...