Frisbees Problem

[canihave]

Hi hope someone can help

I have a load of frisbees to do for a customer, I am pressing nicely on them but the problem I have is the rim of the frisbee warps badly
I have tried on standard press with various pressures
I have tried using my plate press with various pressure
No matter whhat I try they warp can anyone advise where I am going wrong or it could simply be a naff product

Thanks in advanced
Dave