As NonstopOyster0 wrote above, your issue most likely seems to be the default binding for “slew mode”.
On my side, however, the default binding for Slew Mode was not Y, but SHIFT-Y.
So if you press C-S-Y, the sim recognizes S-Y and sets you behind the plane (for using slew action keys).
Please check for S-Y combination on your side. I was in the same situation. I removed that binding and set Slew Mode to another combination and then it was working for me without any further issues.