Do they keep asking for more, however much you already gave them?
Behaviour like this is sometimes called
Relentless, superficially polite demands for evidence that exhaust the target while preserving the appearance of good faith.
Using small technical corrections to take over a conversation and imply the substantive point was wrong.
Putting more claims on the table than anyone could answer in the time available, so that unanswered starts to look like unanswerable.
What would tell them apart
One question, asked over and over however fully you answer it, with nothing you say ever satisfying it or ending it, is one shape. A string of small, correct technical corrections that stops once the point is conceded is a different shape — the correction is what's doing the work, not repetition. Being handed far more separate claims at once than you could possibly address in the time available is different again: it's the sheer count that wears you down, not one question repeated.
Why it might be none of these
Someone asking in good faith will accept an answer, engage with what you actually said, or tell you what would change their mind. A single question, taken on its own, looks the same either way — it's what happens afterwards, not the question itself, that tells the two apart.
None of this covers stalking, doxxing, swatting or harassment campaigns. If any of that is closer to what you're facing, go straight to Red lines instead — the advice on this page was not written for it.