I had extruder jams very similar to yours, but with ABS. I solved this problem by removing the nozzle and leaving it in acetone for a few hours.
One thing I read after that is that a hot end does not like to stay idle at high temperature. Which is exactly what I used to do: in Pronterface I would start heating up both the heated bed and the hot end at the same time. Since on my AO-100 the hot bed takes almost 20 minutes to heat up to 110ºC, the hot end would stay idle at 230ºC for at least 15 minutes.
Now I heat up the bed, and only when it’s about 10º from reaching its targeted temperature do I start to heat up the hot end.
That might be another reason you’re having problems: the humidity. The filament absorbs moisture, especially PLA. See https://www.lulzbot.com/support/support-topics#ex_003
I do not know if it helped, but shortly after my extruder problems I purchased a dehumidifier and keep the room at less than 55%RH. I’ve since been getting very reliable prints.