Given that upstream changes to this package haven't been integrated in
years and this bug being pretty limiting to users, Mobian moved to
systemd-repart. If it's possible for you I might recommend the same
solution.
Our experience has been that once implemented it is far more reliable.
The switch can be seen at
https://salsa.debian.org/Mobian-team/mobian-recipes/-/merge_requests/67/diffs
Key parts:
1. Partitions need to be GPT
2. Partitions being resized need a specific "parttype" UUID configured
on them.
3. A simple config file needs to be installed in /etc/repart.d.
