I posted this in Gary’s milk car review thread, but it may have been a better fit in this one. Against my better judgement, I bought all six of the Friendship PS-1 boxcars thinking I could live with the new trucks since the thumbtacks were gone. (These cars have the new trucks similar the milk cars.)
I put all six of them as a group and ran them through an O72 loop. One or two of them routinely derail in a manner similar to as in Gary’s review. The lead car pulls the trailing car’s trucks off the track and derails it.
I’m guessing blending in some cars with articulating couplers would fix it, but the point of the Friendship Train is to run them as a group.