Some signtool versions (eg. 10.0.22621.0) occasionally fail or never return

Hello,

I have been using the CNG provider (version 0.8) for the past month and it's really nice to be able to continue using `signtool` in our build environment.
What I have noticed though, it that from times to times, signtool misbehaves with the following two potential outcomes:

1. exit with an exit code different from 0 but no error message whatsoever
2. use 1 CPU core forever, never exiting.

This was never happening before we moved to the CNG provider.
I have tried putting calls to `signtool` in a batch loop but have not been able to reproduce reliably.

I'm still investigating the situation, but if this rings a bell with anyone, I'd be quite relieved to learn that I'm not the only one seeing this.