IPSec XAUTH duplicate login

Hi,

IPSec XAUTH tunnel with external authentication over radius on Fortigate FortiVM in 6.4.5.

Devices are trying to establish IPSec connection.

DPD is configured.

Till now it is ok but sometimes if device lost connection or just after reboot previous tunnel stays up and doesn't allow to establish new one. In log we can find:

    XAUTH failed for user "test" 6     user "test" already connected

Connection is idle. Keepalives are being sent but with no answer. Phase 2 is available in tunnel list.

The only option is flush thit tunnel

I tried to configure idle-timeout but it doesn't help.

What other mechanism can be used to make such inactive tunnel down?