Is the temperature always swinging +/-15°C? That is not how a good calibrated PID controller should react. So based on the curve I see (output power would also have been nice) I would think it is just a especially big jump that manages to trigger the decouple trigger. So I would first find better parameter for PID - use M303 with syntax depending on your printer and see if it only swings +/1°C then in normal prints. In edge cases you will always get more e.g. if fan turns on/off it can have a bigger impact.
