Hmmm… I think I found the reason…
Made a new item file and removed the _ in the item
Like this:
Switch garagelys "Garage Loftlys" <light> [ "Lighting" ] {ihc="52571"}
This one does not bring up the warning
But this one does:
Switch garage_lys "Garage Loftlys" <light> [ "Lighting" ] {ihc="52571"}
Is this a bug in OH 2.3??