UI text disapears

After running for an extended period of time, allmost all of the text of the game disapeared. This includes for example: in the flight UI: camera names, total time, time mode, action groups, speed, altitude, throttle, fuel, input sliders; in report a bug window: titel, main text, public/unlisted buttons, account name submit button; in the designer everything exept the main menu. Not effected are: in the report a bug window: thumbnail required and the other phutograph boxes; in the pause menu every button is normal.