Many times a kit which has been stored will become warped. Whether at the stockist or in your stash, pressure or temperature may cause thin long items to warp.
Here are some thin resin Panzer 38 (t) sprockets that were deformed during shipment. The inset shows them after a dip.
The technique is simple and based on the principle that resin has memory. If the manufacturer allowed the resin to fully cure in a true and level mold, the resin will return to the shape it had in the mold if given the opportunity.
I usually boil water and put it into a clear container so I can see the effect of the heat. Here I am using a Pyrex measuring cup as my normal coffee press jar is too unsightly
Note that one must hold the item by the carrier sprue. In the case above, this was not a good idea as the warmed up resin sprocket began to deform from the weight of the water. I had to hold one of the fins between the sprockets and re dip it.
The idea is to dip the item into the water slowly and watch it relax into the proper shape. This means that the item can not touch any of the sides or bottom.
After the proper shape if regained, slowly remove the item from the hot water and dip into cold water. After it is in the cold water, it can be placed onto a towel to air dry.
Here we have Tank Work Shop's British Style Wading Kit as it came out of the package. I did NOT remove the casting blocks and used them as a handle to dip them into the hot water.
Post dip, note the water droplets still on it:
This has worked on EVERY warped item I have except for an Eastern European one which I suspect was warped in the mold. I have straightened out items as delicate as the above to thicker hulls (which warped under pressure).
The bottom line is to NOT touch, push, prod, the piece and allow it to regain the original shape on its own. Believe me, it's memory is a lot better than you can do when it comes to straightening out gun barrels!
Here is a (poor) quality video of the process:
I hope this quick tip is of help.