Op 06-10-2023 om 06:50 schreef Andrew Tropin:
> TLDR:
> abort-to-prompt restores asyncs block level.
> abort-to-prompt from a procedure scheduled with system-async-mark
> doesn't restort asyncs block level.

Looks like a duplicate or variant of
<https://debbugs.gnu.org/cgi/bugreport.cgi?bug=48566>
to me.  (Maybe that's why you put me in CC?)

It has a smaller/simpler reproducer.

Don't have more information, though, beyond a guess that maybe the 
blocking/unblocking is actually going well but due to continuation 
shenanigans, the block level would need to (temporarily) become 
negative, and libguile/asyncs.c is too strict in its checks.

Or maybe I'm confusing things with another bug ...