This cannot be a firewall issue as a loop can be successfully created thousands of time, for hours, before a creation attempt will hang (with no change from the firewall). The rest of the program (other threads) continues to run and there is memory issue.

If I understand correctly, the sockets used by asyncio are internal only and would not be exposed to the world through any local port, so I don't see how a firewall could intercept them (that would be worrisome for all users of asyncio).