Some epoxies will slow to a stall if the temp is just under what they need. Epoxy never doesn't harden unless: your ratio is way off or too cold. If you screwed up with the 5-1 and have it at 4-1 you could get a rubbery hardness. Before you rip it apart, heat the area good with a heat lamp or outside in the sun if it's really warm. I've used WEST in the past and had a mixture stay rubbery until I really heated it up for a good period of time and then it got totally hard.