Render complete dashboards works in 7.0.6 but not in 7.1.1

Hi ! I have problems with rendering complete dashboards. It worked with 7.0.6 - but in 7.1.1 it fails with no error message except “Timeout error”. No chance with increasing the timeout value.

I use the request http://:3000/grafana/render/d/?width=1980&height=1024

It was never free of problems since it worked for any unknown reason only with one of my dashboards, but in Version 7.1.1 it fails even with that one.

thanks for help !