@Developer PM,
Thanks for posting. With my files the problem occurs with both the 32 and 64-bit versions. We've used the VBA cleaning described in my post above and it seems to be working, I originally tried just exporting and re-importing forms/modules but that only fixed one file. I had to use the more thorough process of removing all the code and saving the file as .xlsx, then re-copying the code to fix the other file. I've been doing a lot of testing and currently have about a dozen users testing cleaned versions of the file and so far, I've only had a couple reports of issues, but they're not the same issue and may be unrelated. Interesting though, both the users with issues have the 32-bit version. I've got a lot more users who will be affected whose computers haven't updated. I still have two computers that haven't updated yet.
If you get any answers from Microsoft, please post back here.