Prints melting after curing

[Porchdragon@gmail.com]

Twice now, after curing (the second time was cured for over 5 minutes), I have had a print start melting/disintegrating into a puddle of goo.  I have had other prints stay solid.  Is there something I am doing wrong?

I am using a Mars 2 pro and Mercury plus with water washable grey resin