Neighbor Is Tampering With Our Dryer Vent

Our laundry room is a few feet from the property line, but fully on our property. Our neighbors have complained that the previous tenants used scented laundry softener that lead to strong smells being emitted into their yard. We clarified that we don’t use anything other than standard laundry detergent, and we do a very normal amount of laundry (1-2 loads a week).

A few months ago they put up a large plywood panel saying it was to block the smells from our laundry vent. We said ok even thought it protrudes some onto our property and cuts off our access to the side alley, trying to be good neighbors.

A few weeks ago our dryer suddenly stopped drying effectively. I found a large wad of furniture stuffing crammed into the dryer vent. Definitely not normal lint from the dryer. I removed it, immediately suspected our neighbors, but decided to give them the benefit of the doubt one time and assume they wouldn’t be dumb enough to do it again. Well, today I once again found a huge wad of stuff in vent.

I feel like this is definitely trespassing, vandalism, and endangerment due to the fire hazard? I just want to be clear on what our actual legal options are before confronting them. And advice welcome, thanks!