In-Line Vents on washer drain

Found these two mechanical In-Line vents installed on the washing machine drain line. There is also what I think is an AAV vent at the top. Can I get some help understanding what is going on here. Besides the fact that they are horizontal, why have more than one? Homeowner installation!? Also is there a problem with the standpipe being too short? I see this set up sometimes when the drain line is this high above the washer, is a shorter stand pipe OK? I noted the rubber drain line was bent and water flow was restricted.

Might be o.k., not sure however. I do know those tees should be wyes, though.

Home owner install for sure. Multiple AAV’s aren’t necessarily a “problem,” but certainly unnecessary. Are AAV’s allowed in your area?

The standpipe for the washer is too short. Maybe the home owner thought it was spilling over because it wasn’t vented well enough.

The sewer line is higher than the washer discharge. Many washing machines can pump over 6’ of head pressure. A backflow preventer will help.

I believe 18" is the required length for the standpipe. The mechanical vent would work better installed at the highest point of the sink cabinet above the floor to the right where the other drain is coming from.

Both of those horizontal tees are also incorrect.

I talked to the towns building inspector, the vents are allowed in this town. My thinking, and it’s been mentioned already is that there was a problem with the drain so the owner added more vents. I informed my client that the installation was wrong but it may work.