If you have two open places in ROBLOX Studio (with RibbonUI) and tab out of one and into any other open window in Windows (I am running Windows 7), then some phantom letters appear on your screen, and stay regardless of where you go until you re-open the place you originally tabbed out of.
It seems to happen every time for me if I have two open places in Studio (ie: Place1 and Place2) and then tab out of one of the places. If I go into the other place, the symbols remain, but re-opening the place I originally tabbed out of will stop the symbols. The symbols seem to correspond to the buttons (F for File, 0 for New, 3 for Undo, faded 4 for Redo, H for Home, I for Insert, TE for Terrain, TS for Test, V for View, and P for Plugins.
Upon closing out of 1 of the two places I have open, and going back into one, the symbols disappear and will not re-appear when I tab out.
It’s not the most OHNOES bug in Studio, but this one I can reproduce every time. It is nothing more than an annoyance, but it is a big one.