Extruder1 temperature control

[Sky752]

Good day
I‘m using a PI3 Pro C with SWVer 1.0.04 (Dual Extruder) with RepetierHost 2.0.5.
Manual control via repetier Host is functioning, but when heating up EXT1 (Temp Set 200°C) the temperature is rising above 214°C and then the LCD shows ERR: MINTEMP and on RepetierHost screen the following message: Error: printer stopped due to errors. Fix the error and use M999 to restart (Temperature is reset. Set it after...)
Extruder 2 is working perfectly (same settings for both Extruder)
Any idea or solution?