The automatic dropdown RibbonTab you get when the amount of buttons gets too large has less vertical interior space for the icon + text. In my case this causes the icons to be cut off at the top.
This is caused by the extra border around it, while the total height was not increased.
I think it looks better without the border personally, so removing the border would work best for me.
See attached screenshots for Q2 (might be older actually since I didnt merge my implicit style a while) and Q3 to see what I mean, the button surrounded by a red border is a cutout from the top bar:
- In Q2 the dark gray part matches
- in Q3 the dark gray part is lower then the dropdown buttons.
I checked the default office black style too (as opposed to implicit), this has the same issue.