Carpet printing?

My printer has started doing something really weird. X & Y movements seem correct, but rather than laying down layers, its producing an effect like a carpet with lots of short (1-3mm) vertical thin fibres, look like a tufted carpet or a crewcut hairdo. Any ideas? It started about 5 layers into one print now its happened in a couple of subsequent prints.

Sorted. Not sure how the effect occurred, but realised the only significant change I'd made was the filament, from white pla to what was supposed to be coffee pla. I tried extruding into thin air, it was slow and the extruder drive was labouring. I raised the temperature from my usual 205 in steps of 5 degrees, and I didn't get good extrusion until I got to 230. There was no smell, so I guess it is still pla, but maybe a higher molecular weight polymer.