1031 is not a valid program exit code for posix/systemd

[arnetheduck]

The value of status may be 0, EXIT_SUCCESS, EXIT_FAILURE, [CX] [Option Start] or any other value, though only the least significant 8 bits (that is, status & 0377) shall be available to a waiting parent process. [Option End]

https://pubs.opengroup.org/onlinepubs/009695399/functions/exit.html

systemd in particular does not support parsing values >255:

Aug 16 16:37:42 raspi3 systemd[1]: /lib/systemd/system/nimbus_validator_client.service:49: Failed to parse value, ignoring: 1031

22.7.0

[tersec]

And it's consistent with https://www.freedesktop.org/software/systemd/man/systemd.exec.html#Process%20Exit%20Codes too which is why per #3687 a >1000 code was chosen to begin with, so the usable gap is a possibly non-strict subset of 8 through 199 inclusive.

[zah]

Fixed by #3977 and shipped in Nimbus v22.8.0