When all vmnics are configured to be active and Failback is enabled on the vSwitch, you see that the virtual machine does not return to the original vmnic after a recovery from a connection failover to another vmnic.
VMware vSphere ESXi 8.x
VMware vSphere ESXi 7.x
VMware vSphere ESXi 6.x
The return of a vmnic to service does not necessarily return the traffic from virtual machines to the vmnic that were using it before it went down.
This is an expected behavior, the vmnic changes that occur after a device loss and recovery is as follows: