yep, I can feed as much as I like, temps are stable.
The tubes I added to the extruder are fine, nothing's getting stuck on them.
Plus it's doing it on both normal pla and flexible pla.
I've fettled around with the bed levelling and z gaps - it's not that.
different models, etc

Could it be somethig to do with the steper motor at slower speeds. Dunno.
It's annoying as I could do with having it working at the moment.
Off to the world slinging international in a couple of weeks and I want to take a load of flexible plastic pouches with me.
Guess I ought to just buy printbite for the knp, mod the extruders and start using that more.