Do you use PVC foam as plastic base?
That's what I did, including a material called Forex.
And especially in the places that are exposed to a lot of the sun, this has not proven itself.
Dark colored plastic in particular has shrunk or deformed.
PVC rigid foam is probably not dimensionally stable if it heats up to over 60 ° Celsius.
And that happens very quickly in the sun.
I replaced the plastic with 6mm Medite Tricoya Extreme Durable MDF board in exposed areas.
And I also have a bridge with a beam made of aluminum profile and a support plate made of HPL.