we still had this annoying probleme where we couldn't FLR our backup, source VM could be Windows or linux, with or without LVM... (see error logs in previous thread, overlapping loop...)

latest XOA is installed.

on a secondaray XO CE, I mounted the same remote, and NO PROBLEMS AT ALL... soooo I thought my main XOA is probably beaten up somewhere... but that was not it.

all remotes on main XOA are attached to a XO PROXY (official, not CE) !
on the XO CE that is in another datacenter, I mounted the S3 remotes directly WITHOUT the proxy use, and it worked.

On main XOA, we offload all backup tasks to proxies, so all remotes are attached to a proxy...
I duplicated a remote, same conf, but without proxy, so that XOA would do the restore job, not the proxy, and voila, all is working as intended, FLR is okay on main datacenter.

TLDR : FLR is not working with proxy attached remotes, if you duplicate the remote without the XO PROXY, all good

@florent @bastien-nollet I think there is something to look into.
probably a race condition, the XOA and the XO PROXY both try to mount the loop device ?