What resin did you end up using, was it polyester or was it epoxy? From your photo's the deformation resembles very much the appearance of "shrinkage/deformation" that can occur when polyester resin is used when the percentage of catalyst has been too high when mixing. The highest percentage of catalyst mixed with polyester resin should be 2% IE 20ml of catalyst per every 1kg of resin. Never higher. The normally used percent is approx' 1.5%. The more catalyst above that 2% that is mixed, the more the shrinkage will occur as more heat is generated during the reaction and the associated uneven expansion and corresponding shrinkage with uneven core cooling will happen. The temptation of using a “hot mix” should always be avoided.