After a print failure where the part came away from the bed and got all mangled into my print head (i had left it running overnight). I just could not get my Ultimaker 2 plus to print properly again. I just could not stop my first layer warping and if I did manage to get one to stick using glue the print was terrible, layers were skipping and the head kept getting blocked up after a few layers. After many many many attempts at re-levelling and changes to speed and temperature settings I eventually found the problem, there was actually 2. 1. The cables that power the fan and the head were slightly touching the nozzle fan and stopping it from spinning. This was causing the head to overheat and block the nozzle. it takes very little to stop the fan so if you are experiencImg blockages after a few layers check that you fan is spinning freely. 2. The bars that hold the head are clipped into the guides, the one at the front had become unclipped presumably due to my print failure pulling it out. After I had resolved both these the problem was solved and I again am getting brilliant prints straight onto the glass with no warping or issues. Worth keeping in mind if you are having print problems.