The destroy script lists too many mount points:

		cat /proc/mounts | cut -d' ' -f2 | grep "^$SCRIPT_DIR" | sort -r

If $SCRIPT_DIR has itself been mounted (e.g. a bind mount, a USB drive, an overlayfs, etc), then it will be part of the list and unmounted by destroy, even though this is outside of the scope of alpine-chroot-install tooling. Instead, it should list the mount points that start with SCRIPT_DIR but are not equal to SCRIPT_DIR:

		cat /proc/mounts | cut -d' ' -f2 | grep "^$SCRIPT_DIR" | grep -v "^$SCRIPT_DIR$" | sort -r

Or alternatively, trying to match an extra char in the path with .:

		cat /proc/mounts | cut -d' ' -f2 | grep "^$SCRIPT_DIR." | sort -r