FreeRadius Server crashed when creating a large number of ipsec gateway tunnels.

Hi expert, I am trying to create about 260 ipsec gateway tunnels in my femto test environment with FreeRadius(ver.2.2.0) installed. I prerared 1k users on both Femto and FreeRadius server(as "ipsec.db" and "users" file). However, freeRadius Server crashed during creating the 78th tunnel, and only 73 tunnels were created successfully. Can anyone give me some advice on the reason of this symptom ? Is there any limitation for the number of users ? I attached a PPT file to describe in detail, with topology, HW info and logs. If further info is needed, don`t hesitate to let me know. Any advice will be appreciated. Thank you ! Regards, Li