I do not have very large font, it happens on all functions for me (long and short names).
I found how I can work around it (maybe this will give you a clue.)
Once I click Alt +. and use scroll on mouse so the function with cursor on it scroll away from tool-tips or behind the tool-tip (originally first pop up is directly below function name, touching it), then I can move my mouse away from function name and move it over pop-ups. In this situation pop-ups do not disappear. For #defines positions of tool-tips is the same (touching below), but it is not causing windows disappear issue.
This is not bothering me anymore, I'm just trying to help you debug the product which in general, I like a lot.