In Abbey Road ONE Orchestral Foundations, there are 5 microphone groups. These are as follows:
A group will become active when it has all its signals enabled.
You can tell which are enabled by looking at the active ROM toggles below each signal.
If you then turn up any signal from a different Mic Group, for example Vintage 1 from group C, it will automatically disable both signals from an active group.
This settings can be turned off under the plugin settings > interface. Which is found in the top right corner cog menu of the plugin.