By default, Load balancer uses a Five-tuple hash.
The hash includes:
Source IP address
Destination IP address
IP protocol number to map flows to available servers
Affinity to a source IP address is created by using a two or three-tuple hash. Packets of the same flow arrive on the same instance behind the load-balanced front end.
The source port changes when a client starts a new flow from the same source IP. As a result, the five-tuple hash might cause the traffic to go to a different backend endpoint. For more information, see Configure the distribution mode for Azure Load Balancer.
I believe this is the reason why you may be seeing this behavior. Hope this helps. Let us know if you have any further questions/concerns. Thank you!
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