The PLA filament is fine. I measured the diameter and the number is 2.85mm. I have been using the same filament and setup. I got good prints on upgraded 2+ until this issue showed up. I tried slowing the speed only to 30% but there is little extrusion at 210. If I increase the temperature to 230 and above, it can extrude but the quality of printing is much worse (fragile prints and higher failure rate). I also tried lowering temperature to 90 and then pulling the filament out of extruder to clean up , which seems not working.
Before I made the upgrade from ultimaker 2 to 2+ (changing both the extruder head and feeder), I also had the same problem with ultimaker 2. After the upgrade, the issue does not exist any more for a while. But after using the upgraded ultimkaer 2+ for 100 hours, the same issue appeared again.
I could not got a good measurement of temperature following the youtube video, so can not tell whether the temperature sensor has broken or not. If the issue can not be solved myself, is there any technical support or repair center in US I can ship the product to ?