Occasional failure of Offset2D test under Windows

Occasionally the CI workflow under Windows fails for `testOffset2D`. Always seems to pass on rerun.

https://github.com/CadQuery/cadquery/blob/0b2a075b8c40fe3a546c23b6414a83be1de29c68/tests/test_cadquery.py#L4173

Here is when I noticed the first fail: https://github.com/CadQuery/cadquery/pull/677#issuecomment-791880633

I have chat logs of it failing with AppVeyor and Python 3.6 on 18/03/2021

I don't think there is action to take regarding this right now, but I'll start recording logs in this issue incase anyone else has more insight.