Thunderbird Print Window Problem.

Running LEAP 42.1 with KDE desktop.
If I wish to print a message in Thunderbird by selecting More>Print, the print window is opened beneath all the other open windows. This does not happen when printing from other programs and used not to happen with T’bird.

How do I set the print window to open above the Thunderbird window please?

I have tried experimenting with some of the several hundred possible combinations of window and application (unwanted and not needed) settings but cannot find the right one!
Budgie2