Hi Affan,
When you say it is happening only for few event handlers, then we need to isolate the issue.
1. Why it is happening to only those event handlers? Are there specific parameters causing this issue like specific partner, specific location, specific sender code etc?
2. Does client has any custom activity EH Update Activity function implemented?
3. Check in ST22 any dump during processing date and time.
4. Put the breakpoint in FM /SAPTRX/BAPI_EH_DEL_TID and /SAPTRX/BAPI_EH_ADD_TID and class /SAPTRX/CL_EH_DET_INTF_CNTRL in following methods and process manually event handler through SE37.
SET_EH_TRACKING_IDS
SET_TRACKING_IDS
DEL_EH_TRACKING_IDS
DEL_TRACKING_IDS
Regards
GGOPII