The project was completely blank, only using the generated animator to automatically blend animations. It looks fine if I switch them back to back, but if I crossfade them, it had that little bump up.
I'll give it another try tonight, create a new blank project and redownload the package. If I still get the same issue, I'll upload that test unity project as a whole.
I've tried it again, double checking and redownloading the latest spine runtime, and it's still happening.
I've attached the Unity project containing the animation, the spine runtime, and a scene having the character setup to animate. Maybe I'm overlooking something really basic here, but I can not figure it out. And as I said, if I use the other animations, they all do behave as expected.
Thanks for your time and help with this, much appreciated.