400 - Output variables (columns) must be distinct

[aurreco-uga]

we see this in the logs since Oct 2023.
affecting Ranked abundance scatterplot.
when the user selects certain values on teh x-axis, it get s a 500 (t is really a 400 in data service.)

The problem is when teh x-ais value is included in the 8 values of the overlay var.
THIS IS A DIFFERENT STUDY (check URL) , and the same x-axis value woks...