Mountainous terrain on print (1 reply)

I am trying to print a new X end for my Prusa but am getting large blobs on some corners which are mechanically snagging the nozzle and causing missed steps. I am printing this (Improved X ends for Prusa with clamped rods by jonaskuehling) on a Rostock in PLA and this problem doesn't exist on the first few layers, or after about layer 20. The mountains are on the sharpest bends and are about 0.6mm high. Close up side view of a mountain range in the first picture and a top view in the second to show where it is.
[attachment 15045 Sideview.jpg]
[attachment 15046 Topview.jpg]

I have not seen anything like this before and normal adjustments to flow rate print speed, temperature seem to have no effect. What is specially perplexing is that the problem seems to be limited to a small number of layers.

Thanks for any insight you can give