I don't know if it cover exactly your needs, but here goes my contribution.
I had an issue that was that I couldn't use the keyboard to switch angles while cutting in edit page, only the mouse. What make nuts
is that once it works fine using key 1 and key 2 from the normal pad (not number pad) and suddenly stop working.
After some time I discover what happened in my case: the playhead in the timeline was configure (I did it
) to select the clip on which it is over and this and this disabled that when I switched to another camera, a cut was applied to the timeline. As I understood, this activates the timeline window and not the multicam source.
So, check if it is your case. If so, on the main top bar, expand the [Timeline] menu and unmark [Selections Follows Playhead], then try again. Now woks like charm, as I intend.
For me, this behavior of the software seems to me quite confusing
I hope it was helpful.
Best regards.