Trouble changing bank angle w/ AP sync mode.

[ssn]

Hey,

I can't make the AP sync mode work for bank angle change. Let's say I follow these steps:

1. I fly straight and level, FDs engaged, AP enunciators read: PITCH + ROLL.
2. While holding sync button, I pitch the aircraft 10 deg nose down and bank 10 deg to the right
3. I release the sync button

My expectation at this point would be that horizontal and vertical FD bars update and the plane holds the new pitch and bank. What actually happens is that only the horizontal bar updates the vertical one does not move at all and the plan levels the wings while holding new commanded pitch.

The manual seems to suggest that the plane should hold the new bank angle so my question is: is it a bug or are there some additional preconditions that I fail to meet?

Any help on the topic would be appreciated. Cheers!