Hot end won't get past 180°  

Hot end won't get past 180°

Thank you for reading this-

I have a mk3s which has about 800 hours on it. It has worked remarkable well. I changed out the nozzle and got a few prints out of it. Then one of the wires to the heater cartridge broke right at the cartridge.  I think I was a bit rough on it during the nozzle swap.  I bought some cheap cartridges off of Amazon with varying results.  I also replaced the thermistor with cheap replacements. I ended up buying both in prusa specific parts and it would only heat up to 180. So I bought a e3d prusa hot end kit and installed it carefully.  Same deal. 180ish max temp. Cartridge is seeing 23.6 volts, thermistor is at 100k ohms give or take depending on temp. Using an infrared thermometer bed temps match display temps. I upgraded my firmware to 3.13.2. Did a factory reset. Pid calibration etc. The new firmware gives a "thero anomaly" when trying to preheat..any suggestions? Never gets hotter than 180.  Thanks again-