DNS server reply AA.AAAA.AAA.AA1 andAA.AAAA.AAA.AA2 address for wwww.test.com. Then SG access to the OCN by AA.AAAA.AAA.AA2.
150 seconds later (Frame#5, 6), SG receive the new IP addresses for wwww.test.com but SG still send request to old IP address (Frame#7, 8).
When the DNS server returns a result with a high TTL ("1 hour" in Frame#2), the SG correctly assumes that it can cache that result for the duration of the TTL.
Although the SG does do another query of the name (like Frame#5, 6 in above sample), it seems as though this doesn't update the stored values that other health checks because it is still within the TTL of the first result.
In this case, clear DNS cache or rebooting SG does not help
Overriding the maximum TTL value on the proxy for health checks will make the health checks query the DNS server more frequently.