I can’t reproduce on Linux. And I tried some combination of more threads and more GC.gc. Maybe it’s because I have:
$ python3
Python 3.8.5 (default, Sep 4 2020, 07:30:14)
[GCC 7.3.0] :: Anaconda, Inc. on linux
Possibly I just got lucky (and you on the other systems) and that depends on something, like me havig lots of cores.
You might find the new package:
pkg> add https://github.com/cjdoris/Python.jl
intriguing, and a possible replacement (at least if you have still have a problem after upgrading Python). While the author can’t reproduce my segfault issue there it shouldn’t be a problem, unless you were to use together: