I had very similar experiences with OCIS. Got it all set up following the quick start guide, found extremely odd and unacceptable behaviour with storage space ballooning, start troubleshooting and find “oh you had to do this, this and this manually, it’s in the docs” It is in the docs, but never referenced by any other part of the docs. Because why would you mention the thing that the admin must manually set up in 100% of installs in your setup guide?
Anyway I’ve become that guy ranting on the internet that I don’t want to be. So just so you don’t suffer as much as I did; you have to create scheduled tasks via cron or your preference of scheduler to clean your uploads folder and data blobs. This also did not fix my specific issue and I ended up giving up on OCIS and sticking to Nextcloud.