I didn't intend to imply it was dropped or oterwise abused, I hope it didn't come off that way. Mine was abused and had the same result.

It's a definite weak spot in design by Tamiya. An open-ended metal tub whose cross support is an angle bracket would be fine If the angle bracket connected to a cross brace. But it doesn't, it relies on a metal screw in plastic with little shear strength. Beef up that connection and all is well.

The flaw may never show up under normal circumstances, but require some extra torque or bang it and it's apparent.