Missing route after policy installation on 1490

[mikdemin]

I have a 1490 central managed appliance with two external interfaces in HA mode. I have a NAT-rule in mode "hide" using external standby interface for my proxy-server. For correctly working this scheme i'm also created a static route on my appliance something like the following: 

dst: any          src: proxy-server          nexthop: nexthop for my external standby interface

I don't make any changes in policy and install it. After policy installation missing routing between proxy-server and Internet: ping from proxy-server to appliance is ok, ping from proxy-server to default gw for standby interface is ok (because this network is directly connected on CP), but, for example, no ping from proxy to 8.8.8.8 or something other Internet hosts.

When i disable/enable route the above this issue is resolved. Why is this happening?