@crinrict I managed to capture a video of it happening. This is a bare-bones, new save file. Sorry for the bad quality, I had to reduce it because of the file limits for this forum.
Notice how the sims have their current activity interrupted, stand around in an idle state, then suddenly have an "Argument Anger" moodlet. (Because I was watching for it specifically, I did not continue queuing other actions, but in normal gameplay, you can continue queuing actions while the roommate "stands idle" and both will still receive the "Argument Anger" moodlet after a few seconds.)
I would also like to note that the repeating sounds I previously mentioned in the report do not, in fact, seem to be tied to the invisible argument. My roommate simply went to check the mail and started having repetitive vocalizations (the ones they make while reading mail), and also had the repeating "spray bottle" sounds after cleaning, without any argument having taken place.
@Figblat Looks like the game is stuck during the argument like with homework.
Are there any other Sims on at the time ?
Does it happen if you don't have mods/cc installed ?
Sound issue is probably this then: https://answers.ea.com/t5/Bug-Reports/TO-ADD-CL-Apartment-neighbour-gets-stuck-with-reading-mail/td-p/6024886/
