Yes, in fact it only happens on vocabulary. In fact, it consistently happens immediately after submitting the reading question for every vocab item, without needing to press an audio button or anything. The only thing that you need to make sure of in order to trigger the behavior is that you disconnect from the internet prior to starting the session and remain disconnected. Are you unable to reproduce?
No, it is a different issue I think. The next button is always visible for me. Furthermore, unlike the issue you linked, where the problem only happens sometimes, my problem happens consistently every time. This is just a wild guess since I haven’t looked at the code, but could my problem be caused by the keyboard event listener being on a particular UI element which no longer has focus once you press the info button? I notice that other keyboard shortcuts like backspace also no longer work after pressing the info button, so this seems like it could be a reasonable guess as to the root cause.
Are you able to try using an external keyboard to reproduce the issue? (You would need either a bluetooth keyboard or a usb-c to usb adapter or a lightning to usb adapter.)
To clarify, the problem is that when you have the “exact answers only” setting enabled, entering a word that differs from an existing word by one letter as the answer during reviews just shakes at you (as expected). But this means you can never get to the wrong answer screen, which is the only screen that lets you add the new word as a synonym. So as far as I can tell, the only way to add a word that differs by one letter from an existing synonym as a new synonym is to first disable the “exact answers only” setting. But this means you have to exit the review session and lose your progress. (Using the wrap up option to finish your progress isn’t a solution in this case because it would require you to complete the current outstanding review for the item you are trying to add a synonym for before you have the chance to add a synonym. And once the item is completed, it is not in your review queue anymore, which is the only place you can add synoynms.)
Edit: A good solution for the synonym issue might be to have the info button appear after the screen shakes on meaning questions.
However, I can see both explanations when I access them from the “show all”. 
