Events Manager Plugin doesn't read tables in Multi-DB Intstall

Note: I realize this isn't yen's plugin and not your responsibility to troubleshoot. I'm highlighting the issue so I can track down the problem, perhaps with the help of your team and Event Manager's team.

I have the Multi-DB install set up and working just fine. I am also trying to use a standard WP plugin:

It seems to have a conflict with Multi-DB. It does work just fine without Multi-DB.

Now, the interesting thing is, Event Manager creates its tables proper and fine in the database for the specific site. It also populates the tables fine with the sample data. It even saves data just fine. However, all tables the plugin uses except the Categories plugin are unable to be read by the Event Manager. At least for lists.

Any thoughts on where I can direct them? Do we need to do anything special to use Multi-DB for our plugins that we create? Or is there a specific WP method to read/write tables to ensure they end up in and come from the proper DB/Table?

Kind Regards,