Temperature drop from 208 to 195

Hi guys, i have some problems with my hotend.
Already replaced the resistor, but still it doesn't want to heat up properly.

Sometimes I am pre-heating it for a print and when it almost hits 210 celsius, it suddenly drops fro 208 degrees celsius to 195.4 degrees celsius.

This happens a LOT.

I am running:
- Sanguino 1.3a
- Marlin v.1

Also did the M303 check and input the Kp Ki and Kd codes into the firmware. (I took the second run of M303 results).

Anyone know where I can check for more heating problems?
I'm still a pretty new user.

- Marinus