If the cars physically hit you need longer coupler shanks or drawbars than installed. Likewise if the diaphragms hit or interfere, they need to be cut back or replaced with 'softer' material or more compliant construction.
It's easy to assess truck swing by turning the car over, setting the truck flanges against a suitable piece of curved track or a trammel-cut arc of, say, cardboard and seeing where the truck pivoting might be impeded. What you cut away or smooth to fix the impediment will depend on what you find.
I purchased 8 HO WalthersProto 85' Amfleet II passenger cars for my newly layed track layout that has mainly 32 and 34 1/2" radius curves, but some are 28." Regardless of the radius the cars still derail in various spots on several of the curves. You can see the adjacent cars hitting each other as they go around the curve and not just the wheel truck binding. I thought I would be safe since Walther's claims 24" minimum radius, but apparently that doesn't seem to be the case. Tried removing the door diaphrams, but still have the problem. Tried reading another forum, but really not sure what the fix is or should I just give up and stick with freight trains with much smaller cars. Very disappointed with Walther's on this especially with the money spent and now past 30 day return period.
Appreciate any help
Gary (Coastie71)