Also, you are running a very old kernel, so, please make sure you try to run a
newer xfs_repair.

We installed yesterday 3.10.0-693.17.1.el7. I know that CentOS and RedHat
keep old stable kernel version and backport important stuff: do you think that
upgrading to a more recent kernel (4 and above) would be better,
even if less stable?

Also, this is more a guess than anything. If you see this happening often (even
after xfs_repair), you might want to double-check your storage stack and see if
this is not corrupting anything, bad configured storage stacks in virtual
environments are very usual culprits on filesystem corruption cases.

How could we check our storage stack and see if it is the one to blame?

Thanks, best regards