I had to uninstall the Excel add-on for Logi Options today because it causes issues in column selection. Basically: if there are merged cells anywhere when you try and select a single column, it will instead select all the columns those merged cells span. This wasn't the normal behavior in Excel before installing this add-on, and uninstalling the add-on fixed it. Unfortunately I work with a lot of documents wherein I need to be able to hide and unhide individual columns that may include merged cells, so I had to uninstall the add-on. It'd be nice if the add-on didn't cause this behavior, though!