Same IP Shared between multiple GTM LIsteners

As Pete already mentioned, it is definitely HA configuration issue, If you have not configured MAC Masquerade feature, in L2 requests coming from BIG IP devices, source MAC is always active member's MAC address. So when failover occurs, some switches couldn't clear there ARP caches quickly enough and hence there continue to give away the same MAC in ARP responses. So you have to configure masquerading, this will create virtual MAC for your listener IP which will float with it after failover.

Here is how to configure this feature: https://support.f5.com/csp/article/K13502

And this is very helpful article by f5 about how to choose unique MAC: https://support.f5.com/csp/article/K3523

Hope that helps.

// GIorgi