I have the exact same problem as reported here on issue UE-94316.
Since it’s marked as Can’t Reproduce, I thought my situation, which is not standard, might help.
The Control Rig and the Animation Blueprint are on different plugins. And it might happen that the Animation Blueprint one is loaded before the Control Rig one, causing the variable type of the node to be unknown at the time the AnimBP is loading. I’m not sure, but it might be relevant and a solution may be to save the pin type saved in the node itself (I don’t know if that’s how it already is but, if so, it’s not working for me).