Win 7/64 clients can't Restore Files or Folders from backup

I have a gaggle of Win7/64 clients backing up daily to my DS5100. Recently I had occasion to recover a client’s file from backup, and I couldn’t do it. Trying to Restore Files or Folder from the Dashboard resulted in the following failure:

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So I tried on another client. Same thing. And another, and another. All failed with the same error.

We happen to have one Win10/64 client on the network, and I was able to restore the requested files onto that machine and then copy it over to the original client. But obviously I’d like to be able to restore onto any of my W7/64 clients.

Googling this error message returns many articles fingering various Windows updates (KB3023562, KB3004375 and the like), but the boxes either don’t have this installed, or else uninstalling it doesn’t fix the problem.

There’s an old 2015 KB article referencing a hotfix, but there’s no download link, and the Update Available has downloads only for Windows 8.1 and Server 2012. Neither of those two hotfixes will install on Win7/64, failing with a “The update is not applicable to your computer” error.

Anyone have this problem, and a solution? Thanks!