Referencing Unrelated Data

Looks like you have a join happening on date rather than payment number, hence the PMT approvals summing at a month level rather than a payment level.

Make a calculated column with a related() function to make sure the pmt approval data is coming across properly, and then make the measure based on that (more long winded but you know the join is working by seeing the column). You can then just sumx() to get latest pmt approvals.