To replicate:
1) Under "Visuals" make sure "Combine if possible" is selected.
2) Open and group 2 windows (was able to replicate using several different types... for ex, MS Word and MS Excel)
3) Grouped windows should be full-screen. Close one of the tabs.
4) Groupy tries to revert to "Combine if possible" mode, but does not make the window full-screen. The outer borders are messed up.
