Hi,
1. Looking at SM50 screen your dialog processes are running short.
2. The Roll wait time is high: this is pure indication that your system does not have enough dialog wp.
Total dialog work process = sum of non dialog wp + 1.
If your memory permits than increase the dialog work processes else as a workaround try to reduce background work processes in order to increase dialog and check how the system behave
(you need to monitor the system for background load too).
Regards,
Prithviraj.