Guys, please check your bindings.
Having normal fuel flow in showcase cam mode gave me some thoughts about my bindings, since in that cam mode it changes controls interaction. So maybe check, if you have there fuel flow from both center tanks.
In my case they were the "increase mixture" and "decrease mixture" for 1 and 2 bindings, which I've set both to the same switch. Only difference was the action type "on press" and "on release".