Trouble with 60e. unregister_netdevice: waiting for tun0_0 to become free. Usage count=1

Hello.

I configured ipsec+advpn+ospf between my fortigate's 100d, 60e and 60d. (Firmware on 100d and 60e - 6.2.0, in 60d 6.0.4) Everything worked fine until 60e stopped announce prefix to 100d and 60e. I try connected over ssh to 60e successfully, but the device does not respond to any commands. 

So i tried connect to 60e over console, and i see the one same message: "unregister_netdevice: waiting for tun0_0 to become free. Usage count = 1" . it goesed on until i  turn off power cable. After rebooting i try checked work's advpn and gets the same problem. 

Please help understand whats wrong with my fortigate? Thanks