Sorry we didn't find the root cause yet. Before you reinstall/in-place upgrade, there are a couple last ditch efforts that can be done. First, get your updates current. Using, the askwoody AKB2000003,
Topic: 2000003: Ongoing list of "Group B" monthly updates for Win7 and 8.1 @ AskWoody compare it to your installed updates (not history) and make sure no OS update is missing up thru last December. If any are, then download from the catalog and install. PKCano has been very active for over a month, bringing foward Goup B'ers that either stayed at or rolled back to Dec. These can be found on askwoody Search forTopics>Recently active topics. You need to go back a few pages, now. A good one to follow is
Topic: Win7-Group B. Haven\’t updated since May\’17. What do I do to get updated? @ AskWoody Maybe this will result in kicking something loose on OSK.
Another option is to use an alternative OSK app. There are some available, but the one that caught my eye claims to use the pre-installed one as its basis. It is portable and just right for a pendrive toolbox. My thought was if it fails to work, it might give a more meaningful error code than that by MS.
On-Screen Keyboard Portable Free Download (The download links mirrored to SourceForge for me).
Finally, if you haven't done so already, work out a tested disk imaging scheme. Popular ones can be found on MG
Download Drive Cloning & Imaging Tools for Windows - MajorGeeks Image regularly to save yourself a lot of time, when dealing with the ongoing buggy MS updates. I don't expect MS will change things before W7 EOL.