Iphone Edge Client problem

In our environment, the iPhone / iPad will connect to our VPN gateways from internet to vpn.xxx.xxx.com (IP address resolved by load balancer for resilience purpose), the TTL of the DNS entry vpn.xxx.xxx.com is set to 1 minute.

With Android, the connection to the VPN through edge client is normal even for poor cellular connection (i.e. 3G/4G) with slow DNS resolution speed.

However, for edge client on iPhone (e.g. 2.0.4, 2.0.5), when the 3G/4G network connection is poor with slow DNS resolution speed, the edge client fails to connect to the site occasionally, it just show "Contacting......" and need to try a few more times before connection can be success.

I think there should be some problem with Edge client on iPhone, which assumes a very stable mobile network during connection which may not true in the real-world and lack of a good retry mechanism during first-time logon.

I really hope there is a newer version of edge client on iPhone which can fix my problem.