For what it's worth, I've received this message many times when formatting disks in OMV. I don't know what causes it but after formatting them I can use them without problems.
Like Windfury, I suspect that this is some OMV bug that has not yet been resolved, but from what I can tell it has never affected the operation of my hard drives and I believe that it has not affected any user's either or we would have seen it on the forum.
Unfortunately not in my case,
When I try to create a filesystem, I get http 500 as well with the following error.