Hi, I've been researching this problem for the last few days.
-Hexagon hotend , i3v 10, ramps 1.4, latest beckdac marlin fork
-Hot end normally reaches goal temp in about 5 mins (235c)
-Hot end was gunked up. I removed it, thermistor, and heater. Cleaned hot end.
-Reinstalled everything, thermistor is bottomed out in hot end. Heater is back where its always been.
-now even if I set temp to 270 it will go up to 190 like normal, but either stop there or go up about a degree a minute and might make it to 200 but never higher. Will eventually start dropping again.

I've checked the voltage on D10 and it stays around 12.1 volts even while the temp is going down.

Are there some voltages I should be checking? Could you point me in the right direction?

Any help is greatly appreciated. Thank you