I have experienced similar things with using MSWord activities.
In my case it was exporting .docx to pdf.
What I noticed was that the impacted documents all had settings like ‘tracking changes’ or ‘user comments’. Performing export the steps manually, the save moment triggered a popup, if I wanted to retain the notes in the document. Using the activity, the popup wasn’t visible though.
Since this prompt is part of the save actions of the MSWord API, the Robot is still thinking the activity is ongoing and waiting for it, while MSWord (visible or not) waits for user input. This virtual staring contest leads to infinite waiting times. And since no error is thrown, it’s not directly possible to catch it.
My solution was replacing my MSWord activity with manual steps, including looking for popups and prompts. (Compile it into a new library if you want a single activity again).
Alternatively, if you just want a timeout option on such occurences, you can make a parallel activity, one for MSWord, and one with some form of timeout counter which throws a SE when the end result is not achieved in time.