I can't say I've ever tried feeding wet prey but that's interesting, I might trial that if any of mine ever decide to get fussy all of a sudden!
To OP, with bigger prey like rats (or anything I suppose) at least on my end I'd check that the center / inside is thawed and soft also - sometimes it can be decieving when they're warm and squishy on the outside then you give it a feel and the inside is still cold and sometimes hard, so I always double check but it just means leaving it for a few more minutes. As long as the prey is well sourced, water is clean etc then it's easy peasy.