extruder temp dropping during print

Has anybody run into an issue where the extruder temperature seems to randomly drop in the middle of a print? I’ve been having an ongoing problem recently where every so often, the extruder temp drops by around 20-30C in the middle of a print. That is causing extrusion to jam, ruining the print, and the hobbed bolt strips the filiment. It doesn’t seem related to the specific model I’m printing. I’ve tried with smaller objects with <1hour print time, and larger objects with >4hour print times, and either way it sometimes prints fine, and sometimes stops extruding partway through the print. When it happens, I’ve been just heating back up, pulling out the filament, cleaning up the shavings, trimming and reinserting the filament, and restarting the print, and it generally works the next try. I’ve noticed that every time this happens, the extruder temp has dropped. This seems to happen every 4th or 5th print. Anybody seen anything like this? It’s really annoying, and would be nice to solve.

BTW, should have mentioned, I’m printing with the ‘natural’ ABS from lulzbot, on a TAZ 4 with the hexagon hot-end, extruder temp is 240C, bed temp is 120C. When the problem doesn’t happen, I’m getting very good quality prints (this filament seems really good in that regard).

Well, duh, I realized the temperature drop was due to the startup g-code inserted by slic3r. So something else is causing the problem.