Video "full screen" preference won't stay selected

[RGBNewbie]

Just having an awful time with my shows which I've been running for years without trouble. For some reason my videos won't play full screen, they come on as tiny windows in the upper left corner. I can select to zoom the video, but it won't stay that way. If I go into Sequence Editor and select full screen, then quit, the next time I open it, full screen is no longer selected. How do I get it to stay selected?

[kodiakdjd]

same issue on S4 or S5 . . . 

1st sequence is full screen, next ones with full screen, flicker and seem to start full screen then goes to minimized small box!