Can't remove outdated "ghost" data from iCloud

Hello. I'm trying to delete my iCloud data from my iOS devices (phone and pad). When I try to delete the data, it returns to the previous screen without doing anything. This bug occurs after accepting "permanently delete the data." So, I'm stuck in an infinite loop. The unwanted data is still there.

I removed data from iCloud by logging into my iCloud drive on a PC. It shows zero data. Yet, my iOS devices show that I have 16.6 GB of data in my iCloud. This issue is creating a problem because it seems to be preventing my books and some apps from updating. For example, I deleted one of the outdated apps and tried to reinstall it from the App Store. However, the App Store automatically downloads the app from the "ghost" iCloud data that I can't get rid of.

This problem cropped up recently.

I want to reset my iOS devices, but I'm afraid I'll lose my paid apps in the process.

Thank you for any help you can provide to fix this issue.