185C is cold for PLA. It may work for slow prints, but my personal minimum has always been around 200C and my normal print temperature is usually at 215C.
Long extrusions are probably sucking out all the heat from the nozzle and it's temporarily jamming until the filament can heat up again.
Think of the hotend as a reservoir for heat. For long extrusions, it will drain really fast. Once the hotend isn't printing for a quick second, it will fill back up really fast. At 185C, you are trying to print without a heat reservoir. I mean, it'll work, but not during intense or extended extrusions.