Hi Andrea,

The cluster volumes might have sharding enabled and thus files larger than shard size can be recovered only  via cluster.

You  can try to restart gluster on all nodes and force heal:
1. Kill gluster processes:
systemctl stop glusterd
/usr/share/glusterfs/scripts/stop-all-gluster-processes.sh

2. Start gluster:
systemctl start glusterd

3. Force heal:
for i in $(gluster volume list);  do gluster volume heal $i full  ; done
sleep 300
for i in $(gluster volume list);  do gluster volume heal $i info summary ; done

Best Regards,
Strahil Nikolov