Thank you for bringing this issue to our attention.
I was able to reproduce the bug and after reading through the forum post you provided, interestingly enough the Query works properly when I clicked 'Preview' but gave me the same error you got when I clicked 'Run'.
I will have some folks check under the hood to see if fetch is getting modified, as I do not believe we are using @mistralai/mistralai but can check that as well with our engineering team