I find that the parts in resin kits are sometimes twisted up. Years ago I tossed a resin kit in the garbage because I thought it was too mangled to build. Silly me.
These Sylvan kits are no exception, and every one of them needed to be straightened to some degree before any construction could begin.
To fix twisted up resin parts they had to be heated and then re-shaped. I boiled a couple of inches of water in a pot, removed the pot from the stove, and placed it on a pot holder on my kitchen counter. I submerged the floor and body from each kit, one pair at a time in the hot water being careful not to burn my hands. After these parts had been in the water for ten seconds, I pulled them out with a pair of tweezers and put them on my counter top. The floor part usually straightened out under its own weight. Each of the car bodies had inward bows in the sides, and a couple of them had twists. While the part was still warm, I inserted two metal squares into the car and held them square for about 20 seconds while the part cooled and shaped to the square. Only a couple of them needed to be put back in the boiling water for a second round of reshaping.
With all the parts straightened out, I can proceed to the next step: drilling holes for grab irons.