This usually happens during the printing, It is because the temparature not stable enough and fluctuation. Issue caused by heating tube or thermistor.
- Check if the insulation cotton(yellow one) get loose, It will make temperature fluctuation.
2. Check if the heating wires (red one) and thermistor (black one) get loose, make sure the thermistor screw not too tight.
3.Check if the air plug get loose.
4. Check if the E0 get loose on the board, tighten the screws.
5. If all the wires connect well, Let check if there is issue with heating tube.
6. Check if the mainboard has issue, setting a temperature like 210℃, there should be light on around HE0，
when the temperature up to the same as setting, light will Flash, otherwise we need get a new mainboard.
7.The PID setting not correct, please take a look at the PID adjusting tutorial here: https://help.tevo.cn/knowledge-base/pid-tuning/