"Expressions that yield variant data-type..." error when your Col. is of "Whole number" data type

RiskyBiscuts - I tried using PERCENTILE.EXC and PERCENTILE.INC but same behavior. I also tried every variation of MEDIANX I could think of as well as even throwing CALCULATE in here and there. Couldn't get it to work.

But, where there is a will, there is a way. 

Column 4 = 
    VAR __Table = ADDCOLUMNS(ADDCOLUMNS('Table (19)',"Above",COUNTROWS(FILTER('Table (19)',[Unique Deviation]<EARLIER([Unique Deviation]))),"Below",COUNTROWS(FILTER('Table (19)',[Unique Deviation]>EARLIER([Unique Deviation])))),"Diff",ABS([Above]-[Below]))
    VAR __Min = MINX(__Table,[Diff])
RETURN
    MAXX(FILTER(__Table,[Diff]=__Min),[Unique Deviation])

Brute force, manual Median column. Updated PBIX is attached.

I'm not sure it is a bug.
MEDIAN and MEDIANX return a VARIANT: https://dax.guide/median/

Therefore, they cannot be used in a calculated column as-is.

You can convert the result, though:

CONVERT ( MEDIAN ( Table[Column] ), INTEGER )

This way, you can use it in a calculated column. You keep the risk of a failed conversion to INTEGER.

I think that the reason why MEDIAN/MEDIANX is variant is because they were originally meant to be used with any data type including strings, even though now they are not compatible with such a data type as an input, so I really don't know why they return variant instead of numbers... We should ask to Microsoft about this.