I have some scripts still in bash rather than #babashka because all they are doing is calling other programs. But the one that is in my #guix#mcron was apparently suffering for lack of controlled #ExitStatus. Oi, Bash, I never knew thee.
Yep; just verified. Weeks of annoying error message (actually probably years, but I didn't have a viewport on the output) and it was all ended with a `exit 0`