I have occasionally experienced a similar bug in R21, but it’s always pan that stops working. I can, however, always get it working again by restarting C4D. Since restarts don’t work for you, and I assume you don’t have a protection tag on the camera, I am unfortunately at a loss to help… but I do feel your pain.
Concerning the axis lock/unlock buttons, as I understand them they are strictly for restricting the movement, rotation, and scale of OBJECTS while dragging those particular tools in the viewport, and have no affect on CAMERA manipulation.
I hope you get it sorted out.