BTRFS info: qgroup_rescan_init failed

Hi Guys,

today i found a new error while i was trying to find out why pool capacity and total capacity info doesnt match on rockstor 3.9.1-16:

in fact there are 4x6TB HDD inside in Raid5.while starting to compare the detailed info:

pools:

this looks ok.

shares:


this looks NOT ok. Why is the usage 0 Bytes? 1st thought: quota
so i tried to enable quota (in case it was disabled lately) i found this error in dmesg:

BTRFS info (device sda): qgroup_rescan_init failed with -22

disabling quota results in this error:

BTRFS error (device sda): qgroup scan failed with -4

so i guess there is a problem/bug somewhere.

how to proceed?

btw i’m running: 4.12.4-1.el7.elrepo.x86_64