Update: I found one solution: duplicating the data source, removing all date connections and blending the two. Downside: the action takes INFINITELY long to complete and is unusable.
Something makes me think there is a fixed/include/exclude calc that would solve this but I can't imagine what. The problem is that when a client is selected in the table, that table's datasource only has 2018 numbers. The datasource that is filtered when the primary is clicked has 2017 and 2018 numbers and nothing in 2017 shows up when I click a client in the primary table.
Edit: Solved. I found a few things I could remove from the dashboards to increase efficiency.