I found friction in the feeding tube (from extruder to hotend) was the biggest contributor to the problem. There were two prime issues causing excessive friction that slowed, then stop filament movement:
TPE 60D has a rubber to touch feel. This slips much less than most materials against the inside of the feeding tube.
During print, repetitive retractions combine with issue a) that causes a nipping of the material by the extruder. This causes the filament to expand causing more friction inside the feeding tube.
0.4mm Nozzle @230°
100% infill w/tree support - Cura5.3.0
Clean the extruder
Clean the feeding tube
Reduce the extruder pressure from mean setting for most materials
Reduce printing speed by 50% from above
Optional solution if problem persists:
Reduce the feeding tube length (in so reducing printable area)
Reduce printing speed by 70% from above
Thank you all.
I now aim to make further changes to print down at 0.25mm Nozzle which is out of materials spec.