Extreme lag in IDE (Mojave, 2018r3)

Hi all,
I sporadically pick up Xojo to smaller or cross-platform projects and have started to use it again for the first time in Mojave.
I’m encountering issues with very severe lag when designing the interface in the IDE, to the point that this is unusable.

I’m on a MacBook Pro 17’ (core i7, 16 Gb Ram, Touch Bar) running Mojave 10.14.1.
Clicking on a object in the IDE takes several seconds to highlight it (in the video below, the recording starts with the first click and dragging these objects around is extremely laggy.

Here is a short video capture of the problem: video

Shutting down the IDE, deleting the cache and rebooting into light mode makes no impact
Would be very grateful for any suggestions!

Does it work the same in light mode?
I’m just curios, I don’t have Mojave (still with 10.12.6) and I haven’t done a program with that many objects.

no difference light or dark mode as mentioned (i deleted caches, switched to light mode and rebooted just in case)

Do you see the lag only on that project or all projects?
Can you share your project with Xojo? maybe privately

There isn’t really much to the project; just a handful of of methods for proof of concept for importing .tab file exports from a filemaker database to listboxes; the issue really arose when designing the interface to be similar to my filemaker database - so all that’s on screen is a bunch of radio buttons/labels etc with no other functionality.

I’m going to completely uninstall Xojo and re-install… see if that fixes things. if not will share the solution (privately) but as mentioned it’s currently not even a bare bones app.

It’s the groupbox. I’ve started avoiding using them.

Stam reported no groupbox used (<https://xojo.com/issue/54041>)

Then is that a TabPanel in the video? Because it looks like a GroupBox and the behavior is the same as when I put a GroupBox on the window.

I see the same issue on a 15-inch modell.