Hi Mark,
Welcome to the Forum! Thanks for taking the time to share this. This is something other community users reported and there’s a fix available in the latest beta version.
In brief, we made some improvements to avoid crashes and document corruption when exporting large artboards, but then we noticed we may have restricted it a bit too much, so we made further improvements.
The current limit in the beta version is not tied to the artboard’s dimensions but rather by image format. We recommend keeping exports under 65 x 65 K images. Beyond that, you may see a warning and possibly a slow exporting experience. One of my colleagues summed it up as follows in this post
By the way, I made a test with the size from your screenshot and I could export it successfully using the beta version.
Let us know if you run into any issues