Play Store downloads fail for a subset of applications

I have a problem where the Google Play Store does not download updates for a specific subset of my installed apps. I am using a Sony Xperia Z5 with Android 7.1.1.

When problematic applications try to update themselves in the game store, the download percentage exceeds 100% for a bit, at which time it resets to zero and starts downloading again. Try downloading each application three times and give up. This suggests to me some dodgy data cache somewhere? It also seems that my phone may have problems when downloading the "Google Play security information update" (although I am not sure of this), as I will often see a notification that this file is being downloaded. and go, and then immediately appear and download again. Does this suggest to me that you are doing the same thing as the apps in the Play Store?

I have tried almost all the recommended actions to solve Play Store problems. I have deleted the cache and data, and I have forced the stop in the Google Play Store, the Google Play services and the Download Manager, and then I rebooted my phone without success.

I have not deleted and I have added my Google account again (which is another recommendation for gaming problems) since I'm not sure how much it will cost me to add again.
I tried to update to the latest beta version of the Play Store, but that did not solve the problem and has been happening for about two months.

The only thing that has managed to work, temporarily, is to uninstall the updates in the Google Play Store. This brings me to a very old version of Play Store, but all downloads work correctly. The problem I have then is that Play Store insists that it be updated automatically on a regular basis, at which time the same applications stop downloading again! I'm not sure what triggers Play Store to update or how to stop it. Sometimes it happens pretty fast after backing up, sometimes it takes a couple of days.

My only "solution" at the moment is to uninstall the updates in Play Store every time it is updated again. If I forget that this happened, my phone will happily sit trying to download the same application updates again and again using dozens of data concerts for a day or two (lucky only on wifi). Each time the play store is reinstalled, the "automatic update" (which I have disabled) is automatically activated again.

The fact that it is the same subset of applications that fail each time is also strange. They are a diverse range of applications, some games, some utilities, some educational, so this suggests that it is not the applications that constitute the problem, but some kind of corrupt data / cache problem. Are some Play Store or Download Manager files not deleted when you clear the cache or uninstall the Play Store? I feel that if I could check a log file somewhere, since Play Store fails in a download, I should be able to find out what's going on, but I have a non-rooted phone, so I think my diagnostic options are limited.