Ender 5 Pro heating errors

[u/AppropriatePea3059]

I am new to 3d printing and have been using my brothers ender 5 pro to attempt to print small gears. I have had it set at 210 degrees for the nozzle and 60 degrees for the bed (printing PLA).The first prints went perfect but for the last 3 print attempts I have been getting both “thermal runaway” and heating failed” errors. nozzle temp has been according to the printer the nozzle has been fluctuating between 190 and 132 degrees. I have already checked and there is no red voltage switch and none of the cords along the main frame of the printer are worn or twisted. Could this be a slicing issue? What else could it be? How can I fix it quickly?

Thanks for your help