every single chat dies at about message four

Pattern I cannot break and it is starting to get to me.

I match with someone. I send a decent opener, specific, references their profile. They reply, often warmly. We exchange a few messages. Then somewhere around the fourth or fifth message it goes flat. Their replies get shorter, the gap gets longer, and then it just stops. No unmatch, no explanation, just a conversation that lies down and dies.

This has happened, at a rough count, eight or nine times since March. Different people, different apps, same shape every time.

So the opener is not the problem, or I would not be getting the first reply. Something is happening in the middle bit and I cannot see it from the inside.

Anyone recognise this from either side? If you have felt a chat go flat like that, what was actually going on for you? I would genuinely rather know it is me and fix it than keep doing this nine more times.