> Do you think that pytime.c has the bug? I don't think so.

No, a misaligned stack would be an issue in the caller or compiler, not pytime.c. I have hit misaligned stack in practice, but it should be rare enough to check on init only.

> In theory yes, in practice we got zero error reports. So it sounds like it cannot happen.
> I don't think that it's a good practice to start to add checks in all functions using a clock "just in case" the clock might fail.

My read is that as long as we're not confident enough to remove those checks from pytime.c, a caller should assume they're reachable. If the pytime checks need to stay, adding a Windows only pytime init check to make sure that locks won't deadlock sounds fine to me.