I see a interesting thread on Veeam Forum
where they’re trying to restore .vkb from RDX and got this error:

From your experience, what do you guys think it can be?
In my opinion, the RDX device was broken BEFORE the backup job, or it is a known bug due to the missing update KB4025334 and ReFS enabled on Windows Server 2016.
And above all, RDX in nearly 2022? What do you think?
Let’s flow this thread with our experience in cases like this one, and just leave real solutions on R&D Forums.