HI,
I have an UM2+ that is leaving gaps between the infill and the shells. It has been back to UM and they fixed the feeder that had something snapped inside. However this hasn't fixed the issue. I have tried changing the print temp, adjusting the short belts, adjusting the extrusion width, the overlap and everything you can tweak using Simplify3D and still can't get rid of the problem. I get the same issue using Cura as well. However if I print the exact same part with the exact same settings on my UM2 it prints perfectly. Couple of pics attached. Its more obvious using XT-CF20, but the gaps are there when using PLA.
Anyone got any ideas?