SXT SA5 ac rebooting when nv2 active

I had six SXT SA5 without ac technology working as AP and I lost everyone because of lightning in past week. I changed to SXT SA5 ac with same configuration (with nv2 active). But now they are rebooting after few minutes working (about 5 or more). When I change wireless protocol from nv2 to 802.11, they stop reboot.

I already tried RouterOS:
6.36.4;
6.37.2;
6.38rc34;
6.38rc35;

What am I doing wrong?

Once is enough.
http://forum.mikrotik.com/t/sxt-sa5-ac-rebooting-with-nv2-active/103790/1