I found my project that I was talking about. The actual error was exactly the same as yours, though its reason was slightly different. In my case it was possible that the sought for value is not found and it was quite OK in my case as the obtained value was used in the Validation, so my request is that no error is posted to the log if the sought for value is not found.
In your case, it is strange that the sought for value is not found.
I will appreciate if you create a ticket to Support and let us know the result here.