path = OpenDialogCommandstill no clue
@Miosss in regards to the popup box that sort of makes sense, the VS designer has historically been a pain to work with. What version of Visual Studio are you on? I know some of the later version (16.8+) have had some significant rework and it may be worth taking another stab at addressing the design time of the controls.
For the second issue that sounds like a bug, do you mind opening an issue for it?