Closing main version crashes 64 bit app

I have just updated my app to a 64 bit version which works fine except now when I use to red button in the main window(window 1) to close the app the app crashes! I did not have this problem with the 32 bit version
I have Quit in the window 1 close event. Has anyone else had this problem recently or solved it?
My only work around is to switch off the close button and close the app using Quit App in the App menu.

Don’t do that. Instead, in your app open event, put

AutoQuit = True

Now your app will automatically quit when the last open window is closed.

What I do is get the Close event to fire a timer in App that calls Quit. That way the window is closed before the app quits. This resolves the issue for me.