Bad Behavior with DNS DRV

[于]

I have configured W52P to use DNS SRV transport and it changes to the secondary server when first is down.
The problem is during SIP flows.
   
scenario:
-Server 1 drops
-Call was initiated, invite was tried to 1st server then to 2nd server and phone starts ring on the other side.
-Server 1 on again
-Call was disconnected on the originator side and the Invite was sent to the server were there is no call leg.
In this case remote phone still be ringing infinitely if no FWD or limit is configured. If main server is still down there is no problem because there is no reply.

A good behavior, when failure is detected on the server during register or invite message, is to first register on the second server and then if it is the case send again the invite. Phone should allways send SIP messages (Invite, Subscribe,...) to server where it is registred.
Register Requests should always respect server priority defined on the NAPTR or SRV reply, so every Register should be sent first to the primary server and then, if no response, send to second.

This was the behavior I expect. Is this problem due to bad configuration on my device or is software design?

Regards.