Thank you, linewidth=0 fixed it!
I do feel a bit silly to have missed this, but I'm guessing I unthinkingly skipped over it given that everything was displaying fine in print preview and the normal editor. This might be obvious once you know your way around the program, but it does seem slightly unintuitive to the newcomer. Could I perhaps suggest setting the default line width to something other than 0, and also to ensure that print preview accurately reflects line widths? I notice
a couple of
other people have recently been caught out by this. I get that it's not possible to predict the appropriate width for the drawing scale, but perhaps these changes would help improve discoverability.
Thanks again!