Based on the exhibit which shows an NX-3160 block with marked slots, the correct slot for installing a new node in the existing NX-3160 block is slot 2. This configuration is typically aligned with the chassis' design for orderly expansion and maintaining balanced power and cooling distribution among the nodes.References:
Nutanix Bible, Nutanix University NCS-Core 6.8 learning materials

Ref: https://support-portal.nutanix.com/page/documents/details?targetId=Web-Console-Guide-Prism-v5_10:
wc-protection-domain-wc-c.html

When receiving a field advisory from Nutanix support regarding a rare problem that could destabilize the cluster, the recommended action is to update AOS. This can be done via Prism Element by selecting "Upgrade Software." This method ensures that any patches or updates that address the identified issue are applied directly to the AOS environment, mitigating any potential risks associated with the reported problem. Since the organization uses VMware vSphere, the update specifically targets the AOS to ensure the underlying infrastructure supporting vSphere remains stable.References: Nutanix Support Portal, Nutanix Field Advisories, Prism Element Guide.

Ref:
https://portal.nutanix.com/page/documents/details?targetId=Prism-Central-Guide-Prism-v5_10:mul-security-role