I remade the dispenser asembly using  circles cut from a PVC plate (https://www.gutta.com/product/colured-plates-for-crafts/) which are a little softer than pipe PVC and has a bit of flex. The dispenser is much quieter now. No need to scavenge a large jar lid.

I also replaced the cork with screws in it for a small terminal strip (pic below). It screws on to the motor shaft and you can add additional weight, like a bolt or nail. I get a lot more vibration with this and dispensing is a little more consistent than before. 

It also did not get triggered by rain since I turned the deposit sensor sensitivity down a little. Lot of water in the collection bottle, but no problems. At this point I think I have worked out most of the functional issues I've encountered while testing this thing. 

I still need to move it somewhere else due to the pigeon nest right next to it.

This pic is of the new dispenser during assembly. I have already put it in the feeder and loaded it, so I'll try to post an image of the old and new dispenser assemblies side by side next time it's empty.