Battle Report Close button not operating properly

[HMS ZULU]

while in 'window' mode on return from battle

sometimes I find that the 'Close' button for the battle report screen wont highlight, and wont activate close

 

If I am to reduce window size from full size framed window

the 'Close' button operates perfectly normally

 

the same is true of every other button on the screen in the default 'Lobby' view