F5 GTM - DNS timeouts after several nslookups

I have the same issue. I use 2 listener (2 ISP) to have a HA on my FQDN. When i do a nslookup on a FQDN using this LoadBalancing method (listeners) I have a timeout of 2 sec and after the fqdn is resolved with the IP. When i publish a FQDN directly pointing on the Virtual Server public IP I don't have the timeout and the FQDN is directly resolved.

My listeners are configured with UDP protocol. My Wide IP has a TTL of 30 I set a custom profile of protocol UDP with an iddle timeout of 5 seconds and Datagram LB check.

I deduce that the problem is on the configuration of the HA mecanism of DNS on the BigIP. I don't know how can I resolve this issue...