I've had my first experiences with a PU resin (Xencast P6). I get decent castings but after demolding the casting is sweating an oily substance. Is this always the case with PU resins? I switched from epoxy to PU to increase production, but now I have to leave them sweating a few days and clean the parts.

I am casting a 15mm thick part in a 2-part mould CNC'ed out of Renshape 5173 pu toolingboard. The release agent is Easy Lease. I shake Part A thoroughly before mixing.