In my PBI report I have a calculated table (written in DAX). There is a complex calculated column added to the table. On two occasions, I have edited the DAX in that calculated column, and after ...
Update: I have replicated this with the latest release, May 2020: Version: 2.81.5831.761 64-bit.
It can be replicated in my report whenever there is a click in the formula box of a calculated column on a DAX table, to a header of a column in the DAX table, even on small columns.