Having struggled with this for a while I found a workaround so wanted to share.
Firstly, I followed all the advice with resetting One Drive, clearing it's cache, unlinking and linking etc, nothing worked.
My first workaround, suggested on other forums was to just save to a local drive that is synced with your cloud. Works fine.
But I've just discovered another odd workaround.
If you select save (instead of Cloud save), then when your windows explorer comes up, pick your actual Cloud drive, the project will save fine directly there no issues. I can only assume this is because this uses your windows authentication rather than construct, who knows, it works though.