I have the same situation in 2020 Pro version. Serious problem. After just a few minutes of working, all LayOut commands freeze. (I can save the file, and when I reopen the file, it shows, for instance, the line I was attempting to draw, but it's distorted, like it couldn't keep up with drawing speed. (The line didn't show up at all before I save and close.) While working, suddenly Layout won't snap to any geometry and that's how I know the session is toast.
I'm a power LayOut user and I've never experienced anything like this with SketchUp in 15 years of using it! To have to go back to ver.2018 is going to be a tragedy. I'm using OS Mojave 10.14.6 on a MacBookPro late 2013, 2.3 GHz Intel Core i7 16 GB 1600 MHz DDR3 NVIDIA GeForce GT 750M 2 GB
Intel Iris Pro 1536 MB. Yeah, getting a little long in the tooth, I suppose, (the computer) but I'm not having any difficulty with it on any other demanding software I use. Is anyone else experiencing this miserable situation besides me and Gordon Greenwood? Moreover, does anyone have a solution?