An object lesson in differential movement

My resin caster has been struggling with creating replacement mold for our YMW #105 kit, the ATSF 12 panel boxcar.
As you can see in the photos both of the car sides have bowed outwards and dished somewhat as well.
The caster struggled with trying to true the body up while not altering the pattern, to no avail.
In our discussions he wasn't really describing the issue very well to me, until he actually sent me a photo.
I instantly knew what the problem was.
The actual car sides are resin castings, laminated to styrene backers. Now the pattern held up well for the first couple of years, but it's now been in the hands of 3 different casters in rather climatically different parts of the continent, so I'm not at all surprised.

Styrene and resin have different expansion and contraction rates. And this issue with the pattern is why I strongly discourage resin builders from using a lot of styrene inside their models for bracing, etc. Under the right conditions, glue joints can be broken and new kit results.
So, as you can see, buttresses are being inserted and the car sides should straighten out and we can get the model kit back in production.
I have a few very patient customers with this kit on back order.