Hi Tarun,
Have you checked my suggestion on this thread?
1. Check sales order holds more than 30 line items and trying to update in one event handler. We had this issue before in Shipment that caused queue blocked. This would happen most of the time in peak hours due to resource work process allocation also and same event handler locked to update.
2. Go to my suggestion which I mentioned in this to check "TID" in queue, take the sales order and find event handler how many events trying to update for one sales order event handler in SAP EM.
3. Also, Go to SAP EM and check any Lock event handler program running long in the system, that may blocked processing event handlers
Regards
GGOPII
