AISense_Sight lost when seeing more than 5 character

I am getting start with AISense_Sight, 1 AIController and 5 Target work fine.
After adding 2 more Target become 1 AIController and 7 targets including player, the AISense_Sight get lost sometimes because of Sight’s Age != 0 .
The situation more serious when the player controller gets far away from AIController but still in range.

Engine Version is 4.16.1
Computer platform is Win10, AMD1700X, Nvidia 1060