Finding duplicates dates across multiple columns by category

Hi all,

I'm having trouble finding a way to find the consumers who have duplicate dates in multiple (2 in this case) columns.

Data collected and imported like this:

And I'd like to be able to identify the duplicate dates by consumer ID:

Here's a non-exhaustive list of things I've tried:

I separated the table into two - one for date column A and one for date column B, using SUMMARIZE COLUMNS and tried to match them from there but I kept getting errors. I matched the two tables on ConsumerID. They didn't like that. Then I tried one to many matching from the two ConsumerID columns to the parent table 'Consumers', and I still was getting all kinds of errors.

I *even* tried unioning the two tables and trying to manipulate the data from there:

I think this shows some serious gaps in fundamental knowledge on my part perhaps with row context vs. filter context, but I was hoping I could find a solution to this issue in addition to some suggestions for dax concepts to better familiarize myself with.

Thank you all!