Instek GOS-6200, no more delayed sweep operation

[wodi]

Can someone help me to find out what's broken on my GOS-6200. All  functions are available except delayed sweep operation. I can mark the specific part but no magnified graph is visible even not in trace sep mode. Unfortunately schematics available at download links are not readable good enough and at page 12  half page is missing. Many thanks for any hint what to check.