If the LAG port is being used as a management interface, you may need to access via CLI and recreate the interface. Syntax would be similar to this example:
Example: create <topology name> physical <vlan id> port LAG1 <tag]untag> <ip address/mask>
Example: create Mgmt physical 100 port LAG1 untag 22.214.171.124/24
This is fixed in version 4.76.05 and newer.