One neighbour left the area after having acid thrown on their car.
One neighbour received letters many years ago and they didn’t even have a dog.
Over the last 11 years we have been the main target.
Although in Feb 2023 a neighbour nearby had their fence painted with the word ‘dog’, their car spray painted and a letter saying their dog was always barking.
Mid that year, they went to Europe for 6 weeks, and had their dogs cared for at another house. They got letters during that time saying their dog had kept this neighbour awake with barking from 2am-5am
Sounds like it someone who is very local and knows that the block next door is empty. It might be worth investing in an extra camera trained on the neighbours house. The persons involved sound disturbed and dangerous, you should notify the police.
Get a couple of camo trail cameras and mount them in your neighbours house or ask the neighbour across the street to install a camera looking at your house.
Can you see people walking down the street past your house with your cameras? What about your neighbours that you can talk to? A friend sometimes has the police ask her for footage from her cameras if something happens in her street, not that she has the incident on film but just to put the perps into the location at the time. You might have a neighbour that has someone walking past their camera on the way and the way back within a few minutes on the night that you had a visit.
I don’t have any of these but have seen images from some cameras including a bushfire that burnt part of a friend’s block but got ours. Most are designed for wildlife so the night time images are good. I would probably go into a shop and ask someone who has knowledge of them and get one that way. Another thought is to go and see your local council and talk to the Local Laws Officers. Most would have some cameras for catching people dumping rubbish etc and you may be able to hire one for a couple of weeks.