What washers are supposed to be on the top of thunders? I have a set of thunders that I got second hand so I have no idea what bushings or washers are on there but I'm getting some washer bite on the hanger from the top washers and that don't seem right.
It also might explain why I like these trucks less than my others. They seem stiff and don't seem to turn very well and maybe that's because they're not able to lean as far as they could if I had the right washer on there, maybe??
From doing a lot of swap and trade of second hand parts, I notice that however the previous owner set up the trucks, they will have certain things happen from that, eg tightened down bushings are squashed and just don't rebound as well as others, which could be the case here for you.
Even taking everything apart and checking over the bushings, wax the pivot point of the hanger and clean off the bushings, which then will often make things feel way more "normal" to me, especially if a set of trucks doesn't feel like it turns as it should.
Not sure what else you have on hand in the way of other spare parts, but you could swap over washers from some other trucks and try those on the Thunders instead, just as an option. Like all sets of trucks, the top washer is smaller than the bottom washer.
Most skate shops should have some spare washers too, or at least all the bushing kits have washers with them, be it the Thunder rebuild kit, or Indy bushing kits - those washers especially are very flat, compared to some of the deeper washers that make the sort of contact with the hanger that you are showing in the picture.