Check the entire thermistor cable as well as the plug connections for tightness. Preheat the hotend and then wiggle/bend the cable 1 inch at a time all the way back to the main board plug checking to ensure the recorded temp remains constant. (You can also do this with an accurate multimeter checking resistance across the unplugged thermistor if you don’t want the printer on while poking around.)
Those aggressive jumps sure look like a thermistor problem, but only when printing in motion, which screams bad cable/connection. Manufacturing errors happen.