the individual blocks work, but trying to render an area makes this

No, this is certainly not supposed to work this way - some error is clearly occurring when it tries to build the area mesh. Can you send me you latest.log file? (Check https://fabricmc.net/wiki/player:tutorials:logs if you don't know how to find it)

Cheers

can you confirm that you have received it?

I cannot, in fact, confirm that I have received it since it appears you did not make the file available to everybody with the link. I'd personally also be fine if you simply uploaded it here on GitHub as an attachment to a comment

Cheers