We are having issues running a Bot that uses WinHllapiAdapter Text Adapter (Screenshot attatched). The strangest thing is that our Bot have run for months and suddenly this error began to appear. We have tried resaving the automation and re-interrogating the screens but the error remains. We have checked that the screen is correctly defined in the TextAdapter.os (Screenshot attatched).
I believe your issue is with the automation. It seems as though it is corrupted. I would recreate the automation and delete it from your existing solution. It must have changed which left something behind that is not valid.
If you do have your code backed-up, you can compare your current copy of the os file (or better yet, the copy where it first started with this error), to the working copy to see what in the os files are different. Use a utility like WinMerge or another file comparison tool to examine the XML for differences and that might help.