Having multiple copies of the database is a symptom of sync conflicts. Of course it's never actually Keepassium which can help that as they never were responsible for the sync, but that won't help you if suddenly you have 3-4 databases because of sync issues and must analyse the differences. So in theory the concept of Keepassium to let the dedicated apps in combination with ios files handle the syncing is nice, but in practice it seems so lead to issues at least for me. Google drive seems to only work when online according to the guide.

Onedrive just started working again after 2 month of issues if you can trust the threads. Looking at the reddit, there seems to be issues with ds files sync and synology drive is not supported. Why does it happen? Not sure, but for Dropbox I need to go into the ios files app and view dropbox there, otherwise Keepassium just kept using some old cached datebase (without a warning).

Even though I merged them using KeepassXC, in the end I was somehow missing an entry. Personally I had issues, was using dropbox to sync and multiple times I ended up with 2-3 database files.

Keepassxc for ios