It could be that the data is partly stored on cache disk and yet to be move to the data disk, what I've tried is to do a quick sync up between those two directories.
```
rsync -a /mnt/disk1/appdata/postgresql15/ /mnt/cache/appdata/postgresql15/
```
Then restart the container and it's started as expected.
Note the disk number in the above command, yours could be different, and make sure to make a copy of those directory for backup first.