Re-freeze

[FranklinMorphs]

I see two reasons not to do it.

Firstly, there is the same reason as any food. As you defrost it and re-freaze it, you separate water in the rat, as with any food, and the re-freazing causes those water molecules to bond and freeze, which simultaneously dries out the food, and can damage tissues, causing the texture to be damaged, in this case, the rat can leak and get really mushy.

Secondly, there is the possibility of contaminating the rat during the defrost, attempt to feed, re-freeze process and freezing, unless well below true 0, will not necessarily kill everything, though it would slow it's progression, you could inadvertently introduce something harmful to the food which just festers while frozen and may go absolutely nuts when re-defrosted, and could make your snake sick.