WorkFlows stuck in error NR 889 - No Free Interval Found

Hi Experts,

Approx 800 odd Workflows tries to send IDOCs (data flows) at the same time and approx 50 of these workflows get stuck on that step with error message NR 889 - No Free intervals found.

We restart these workflows later through transaction SWI2_DIAG so that all the IDOCs are sent in time, however a permanent solution is required for this issue so that workflow do not stuck in this error.

Please suggest.

Regards,

Nidhi