No suggestions, as I haven't figured stuff out for Calvin. However, I found, unless we're in the Eagle. Calvin does not travel well. He starts out fine, eats his snacks, but once we get to the motel. He won't eat, or poop the same as when we're at home.
It's been years since he joined me, but, IMO, for whatever the reason, he still thinks he's gonna go to another home. As it was the case during the first few years of his life.
He won't go to the back room at the clinic. For some reason, or I think he remember's .... well, he remembers, I think.
Good luck,
Pops