I just had the same issue. Because you mentioned about Cura 2.6.2, I was able to find a workaround for my problem. Hope this helps you as well, if you haven't already figured it out.
This happens only for the 'custom printer' profile. If you select any of the existing machines included in the software, you won't get this error. I tried changing the 'machine settings' of my new custom machine, but no luck.
But the custom machines which I had added a long time ago in the previous versions of Cura (which then were automatically migrated to the newer version when I installed one) were still wo