Progress bar display issue

I don’t develop much for OS X. I’ve noticed that when a progress bar is full and a modal type window like GetOpenFolderItem("") is triggered that the progress bar will appear empty.

Thoughts on how to avoid that or confirm that’s a bug or non-issue?

I don’t see that behavior. If I have a full ProgressBar and open a modal window, the ProgressBar turns gray (instead of blue) because the window no longer has the focus, but it otherwise does not change.