I would not scratch my head for too long if I were you, it’s just a fact that CC does not like files with a (very) large number of objects, my guess is memory management code is sub-optimal.
Back in the day I hit this limit twice, first doing this:
and later trying to load the DXF for the “Aztec Calendar”…it brought CC to its knees. This is when I decided to switch to V-Carve, and it handles the same big file easily.
CC is a GREAT tool, but it has its limits, and this is one of them…