Broken Temperature Sensor ?

[SpaceKnight 0]

Hi,

i wanted some feedback for my problem analysis.

 

Printer: Ultimaker 2+ with about 8000h print hours

 

Everything was printing fine until suddenly i let the printer sit for holidays. When i came back nothing would stick to the PEI plate. I cleaned and tested everything. ( Extruder cleaned, build plate cleaned, new Nozzle).
I noticed the filament did not flow fast enough at the start of the print so i started turning the flow rate up and heard the extruder could not keep up. Following that i upped the temperature of the nozzle in 5°C steps until i hat 20°C+ and it suddenly worked. With that knowledge i suspect the temperature sensor is broken. I measured the thread of the block (with out a nozzle) a difference of 30°C. (Printer shows 210° reality 180°C) 

 

Is my conclusion right that the sensor is broken? Is this normal that this happens? Is it possible to just change the sensor ?
Thank you in advance :)