There was a lot of inconsistency with the DI Maxi IVs. I've got a bunch, and it seems like each set is a bit different. Perhaps had there been another run that would have evened out.
Some of the cars ran perfectly right out of the box. Many required the fix kit. Many required different solutions. I just played with them until everything worked well and they are the major part of my intermodal fleet now.
After seeing Gary's Kato Maxi IV mods I almost regret selling off my fleet a couple years back...
But my DIs run well, and the Atlas 53 singles run well, and the JTC singles run well, so life is good! And Oh, yeah, I still have some of the old Walther singles around (with the Gold Medal kits - and they're fine also.