Temperature change cause seams to reappear?

13 piece 3-D print. attached all pieces. used bondo and then painted.
Live in Nebraska, took the model on the road and the seams are all starting to reappear.
Any thoughts? Anyone know a premium type bondo product?

Try Stabalit Express - its a two part acrylic (Powder and liquid) and the results are brilliant - easy to over paint and sand!! Full cure takes about 20min, significantly stronger than the original 3d printed part

Appreciate your help!