Sourcetree will not restore after minimized

After the last update, I now have the following symptom: 

I run SourceTree and it seems to work fine.  I minimize it, and then later go to restore it.  It does not restore.  This is consistent and happens every time.   Instead of restoring, I hear the windows beep that you get when you click on something out of focus - maybe there is a dialog that is hidden that is blocking it? (Though I don't see any such dialog when I Alt_Tab and look at the preview, it does sort-of behave that way.) 

I try Alt+Tab, and I can tab over to Sourcetree, but it still does not open, (I just hear the beep).

If I right-click on SourceTree in the task bar, I can close it with the "X Close Window" option, and then it will open fine again.  This is the only thing I have found that helps.

Rebooting the computer did not seem to help.

This issue does not occur on my second PC, even though the setups are identical as far as I can tell.