Unofficial Skyrim Special Edition Patch

If I understand correctly the issue you are describing then this is a known bug from 11/11/11. It's referenced here. I think it's "Changing locations while in mid-conversation with an NPC sometimes causes the NPC to follow you to that location."
Looks like a recent & very simple fix was discovered: https://www.nexusmods.com/skyrimspecialedition/mods/66998/
Please try it, and report.

While it is indeed an instance of that, in this case, it has negative consequences to the quest; it's not benign like most other cases are.

Sorry, I think I totally misunderstood. This is a totally different issue.
It would probably be safe to disable player control when the conversation triggers, and give it back at the end. Just like when you meet Aela for the 1st time in the farm exterior along the road to Whiterun.

LOL, I filed two different bug reports for different issues around this quest and never noticed which one you were replying to. Your first response would've been an appropriate response for the other report, so I just assumed it was that. I agree, locking player control would prevent the issue for this one.

Changing that setting to disable the mechanic would be a disaster as it would not just affect this particular quest. It would have ripple effects across dozens, if not hundreds, of dialogue responses. That would make it too invasive to be considered at all.

Disabling the player's controls is also not an acceptable solution.

I hate to be that guy, but at this point anyone playing Skyrim should be aware NPCs will do this and the answer is pretty simple - don't set out to break things on purpose by intentionally dragging an NPC through a load door. Just wait for them to finish and then move on.

I think we're all getting confused between the two bug reports, which are two entirely different problems that happened to arise from the same event. For the problem of Eola's dialogue overlapping, could it not just be set to be "modal", to use the programming term, so that once she starts, you have to listen until the end? There's a lot of dialogues that are like that. That seems like it would solve the problem.

I'll reply about the other issue on the report where it's relevant.

I just read your reply in the other topic and responded to it. I think there's still some confusion here, though. The issue with Eola is NOT a "dragged into the wrong cell" issue. Hell, I'm not even sure if Eola's the speaker, so I may have caused some of the confusion. So, just to be clear, here's what happened:

* I entered the Hall of the Dead and the voice-over started (I think it's actually Namira speaking, not Eola, I just got confused).
* Then, trying to ditch Verulus (as per the other problem), I left the cell and re-entered. The main point here being I left and returned - Verulus himself was irrelevant. I could've done it just as easily if I'd changed my mind and then changed it back or something else like that.
* When I re-entered, the voice-over started a second time, leaving two completely incomprehensible voice-overs running at the same time. I have a feeling I could've left and re-entered a few times and gotten a whole crowd of voice-overs. At that point, though, it would definitely be in the realms of deliberately breaking things.

An easy solution (I think) would be to have a variable indicating that the voiceover has started already, then don't trigger it a second time if the variable is set.