iCloud Error / bug "file does not exist" BUT IT DOES!

I regularly get errors when trying to open pages / numbers documents that are stored in iCloud.

I navigate to them in finder, finder shows correct info, name, size, last modified etc.

I double click, it shows it is downloading then the error comes up:

"the file does not exist"

It clearly exists. When I double click on it again, it will open.

It's like a big that numbers / iCloud / MacOs can't wait longer enough for the file to download?

(they are not big files!).

Any ideas or is it just another example of Apples increasingly bugginess?

(yes I pay for extra storage, that is not the issue!).

I also get iCloud sharing errors - will post about those separately, though it may be linked?