You’re more likely to get help in the UnRAID forum than here in my experience unless you can prove the issue is PMS and not UnRAID/Docker/Docker Container.
I’m no container author so I could be totally wrong but could it be the order of the mapping args passed to docker?
Does docker support splitting out subfolders like that after defining the parent folder?
My brief googling didn’t turn up much but I’m probably not using the right terminology.
Actually looks like hotio wants you to use his discord for requesting support, I’d start there and make sure what you are doing is supported by the way he builds his containers.
I’m running unraid. Honestly if it’s still being written inside, you may not have exposed your folders correctly. From unraid from the command prompt, you should goto the new locations and see if anything is being written there. If not, your permissions or mapping may not be correct. This is really not an issue either plex, hotio, or unraid can answer. Your basically doing some custom docker work