Got it. Did some house cleaning and removed something that was conflicting. Not actually sure what it was because I removed a bunch of stuff no longer needed.

Had an extraneous Worksheet Change Sub later down in the sheet from previous work, as well as some workbook code that was no longer needed. Removed both along with the hidden columns and one of those did the trick.

Thank you both kindly. For others for future reference, I opted for p45's in the end as it seemed a bit lighter on a few initial tests for my particular setup.

You can safely hide the columns again.