I live rurally but there are a couple of houses close by to mine. One neighbour is very anti-social. Lives with her parents (they all moved from London a couple if years ago), barely go outside (including prior to Covid). She is late thirties, parents are late fifties (I think, I've only glimpsed them twice).
It's become her habit to send me a text message complaining about something every few months. This time, it was a complaint about occasional mis-deliveries by Royal Mail and delivery drivers to her home that were meant for me. In the countryside this happens all the time, and I just put their parcels and letters over their gate. But oh no, the way the text was framed is that this was a serious misdemeanour on my part and I needed to take action" to make it stop. Of course, I messaged back pointing out that it was me who had been bringing round their misdelivered mail.
The previous time, it was my small compost heap miles away from their boundary that was "causing smells". Again, a bitter series of texts, full of accusations. It turned out to be their own blocked septic tank that was causing the smell.
Prior to that, it was hedge trimmings blowing onto "their drive". I actually own the land and they have a right of access over it! And I'd been trimming the hedge because they don't!
Prior to that, they tried to get out of a mutual maintenance payment, claiming that because they stayed in and barely used it and get their shopping delivered whike I and the other neighbour have 2 vehicles, they shouldn't pay their full share!
How to deal with? They seem to have a fixed notion that I'm a problem that has to be sorted out. They don't interact with other people at all and instead all 3 of them sit cooped up in a small house thinking up strange ideas.