MSP430F6779: It's easy to reset when EFT & ESD testing

Hi! 

I use the MSP430F6779 in the three phase electric meter project, it's used in the the industrial application,such as switch cubicle, power distribution room.

The RS485 is SN65LBC184.

When the 4KV EFT test,  HBM 8KV ESD test, air 15KV ESD test, the MSP430F6779 is easy to reset. Why?? How  to improve it ? 

I heard that the ST's strong anti-jamming capability, can pass the EMC, EFT, ESD, Surge test. the P/N is STM32F103, STM32F407, STM32F7--.