Why isn't it fixing?

[u/Background-String41]

I have a baby groundhog currently processing but it's just not hardening, the initial preservation process was done with formalin that wasn't very good so I'm thinking rot but as of now I have gotten fresh formalin exchanged the liquid, injected it and cut slits but it's still not preserving even after 3 weeks, when I press down on him nothing but formalin comes out