does sound a bit over worked. maybe best to let it rest for a while, so it can cool down.
i use crisco on my board, but corn startch works well too as does icing sugar - depends what works best for you. but it might be worth trying something different.
what kind of gumpaste is it? store bought should be pretty fault free, but if its home made, it might be somethings been left out or the recipe is a bit off.
xx
Gumpaste doesn't need to stay in the fridge, it could be that has helpe to create problems.
xx
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