I created a canvas based control, and in the Inspector Behaviour I unchecked a number of properties that shouldn't need to be changed...
I saved the project, ran it, tested it, and then came to the conclusion that I needed to set one of the "unchecked" properties to a specific value
I went back to the Inspector Behaviour and lo and behold, all the unchecked items (except for Super) were GONE
I loaded the project into Xojo2016 and they showed up, I checked the ones I needed back, saved it in 2016
when I loaded it back into 2018, they were there again.