I had a similar issue occurring. It was frustrating on long prints. The problem has been resolved for me and I think it was several issues occurring for me. I tried many things to resolve it including new Bowden tube types as well as the "grabber"One was to much pressure building up within the extruder. Reducing the flow control can help here. When your temp drops you may be experiencing this. Have you tested your thermistor and are you sure you have the right thermistor defined?The second for me was the Bowden tube did not have much slack for prints that were at the extreme of the radius. This caused it to slowly work its way out over time in long prints. Using a longer Bowden tube help resolve that.