So I should remove the one I have included, and I suppose the Xojo built-in one gets updated from time to time? Mine doesn’t of course. 
Thanks, Greg. While I didn’t know this, it is not surprising. However, I find I’m still better off with the external classes. Without it I still see some weirdness, notably in pushbuttons. When I get a little time I’ll make an example for Feedback.
Tim, don’t dump it just yet 
No indeed. I tried dumping it and also removing the initialisation code from my app’s startup, and setting Normalise to on. The result was I was back to having no correction of controls at all.
Or does @Greg_O_Lone mean that having the Normalise switch on mean that ModGTK3 is included, but that one still has to initialise it?
Setting the switch to true also initializes it when your app starts. It is meant to be a set and forget kind of thing.
I checked the version we have and it’s from April 2020. I see that there has been a few checkins since then.
Mmm, that’s what I thought. When it didn’t seem to work I rapidly restored the previous saved version from Time Machine.