Dog and onion tops in garden

[Beansandcheesearegood]

Looking for advice.
I've posted before about my neighbours asking me to stop my dog wagging his tail on the fence.
We have a slightly strained relationship with them- they once asked - well shouted at my dd to stop playing football in the garden too. We do still say hello abd acknowledge each other but not too much more.
Recently the dog has been 'finding' sliced onion tops near their fence I've thought nothing of it- they're gardeners maybe used for that, or compost? I dint know. But today I saw 2 sliced onion tops laying on patio about a metre or more from fence- first thing this morning- obviously I binned them so dog not eaten them. I'm starting to think they've thrown them over....although they're grumpy older people I would never think they were trying to hurt the dog... but I can't think how else they got there! Not sure whether to knock and mention it- or wait to see if happens again....

They want you to tell your dog to stop wagging his tail next to the fence? What are you supposed to do, threaten to ground him if he shows any signs of happiness in certain areas of the garden?

The onion thing I’d be slightly more concerned about. I think I’d be inclined to mention it to them the next time you see them. Not accuse them, but ask them if they’ve had any issues with things being thrown over their garden. Tell them you’ve now got cctv covering the whole of your garden now, so if anything else comes over, you’ll be able to see which direction it has come from, and can then put cctv up to cover that area too, so you can let the police know and pursue them through the small claims court for vet bills if the dog gets to them before you do. Obviously reassure them that nothing is covering their property but that you can recommend a really good camera if they’re having the same problem. Tell them it’s so good, it even picks up hedgehogs in the garden at night.

I’d also start collecting snails and the roots of blackberry bushes to lob over the fence every time they go to the shops. But I’m a dog person.

Thank you @WilfredsPies I'm trying not to over react as I love my dog obviously so trying to calmly think of other explanations but honestly can't.... the cctv is a great idea! Thanks