Native resolution on the Surface Pro 6 is 2736x1824. It wasn't an issue with 1.37, and only became a problem after the 1.40 update.
I'll grab the log file and sent it through shortly.
Or as it turns out, I won't send you the logs, as everything now works as it used to/should. This computer apparently wants to be temperamental. In future if it misbehaves at all, I'll exit the app, copy the log file aside, and then try it all again - maybe there's something not quite right when it first starts up. 🤷♂️
Thanks for taking the time to reply - I'll be sure to put my local instance through multiple trials before crying wolf 😊