VPN zombie connection

[Steve]

Sometimes iOS AnyConnect VPN back from sleep, it seems the connection
still alive, but could not  reach the VPN gateway, after disconnect
and reconnect, the VPN works like normal again.

Log shows a lot of:

Feb 24 22:35:20 AA ocserv[16757]: main: unexpected DTLS content type: 23

Feb 24 22:35:20 AA ocserv[16757]: main: could not determine the owner
of received UDP packet

Feb 24 22:35:23 AA ocserv[16757]: main: unexpected DTLS content type: 23

Feb 24 22:35:23 AA ocserv[16757]: main: could not determine the owner
of received UDP packet

Any suggestion?

Thanks.
Steve