Sansa e280: showing only white screen after starting Rockbox

[mb2105]

Hi, since a few weeks my Sansa is showing a white screen after starting Rockbox. The voice is audible. After a few minutes of playing music the Rockbox screen appears correctly and stays on. I reinstalled anew after formatting the player but there's no change. The white screen also appears when connecting to PC. I have to switch it off (press menue button 30s) and on a few times to get the display working again. This is extremely annoying. Is there a way out? Please help.