I have used Athearn Delrin trucks a lot. A solution to the leaning on many cars is to put a washer in on the screw that fits inside the truck bolster. Walthers makes/sells a 2-56 brass washer in little packets of about a dozen. The ID works great with 2-56 screws, either wood or metal threads. The OD just fits the inside of the hole on Athearn bolster.
The problem is that the top of hole inside the bolster on the athearn trucks is not level or flat. It seems to be curved or beveled. The washer fits snug enough to create a flat surface for the screw head to tighten to.
The same washers work with Weaver trucks. I am not familiar with Wiseman.
If you look at the top of the athearn bolster, it has a ridge which I think is intended to mate with some bolsters.
I have used this technique on Wood cars.
A more aggressive approach if you have one that this does not solve, is to get a spring that fits into the hole in the truck bolster and around the body of the screw. The spring has to be soft enough to compress when you tighten the screw and still allow the truck to swivel. Finding such springs is very hard. I have done it a few times from my parts box. I know of no commercial ones.
