Failed to set file group

What could be the cause of this error?

Quote

Failed to set file group to 'users' for '/srv/dev-disk-by-uuid-7F9B-F0BC/backups/': Unknown error

OMV\Exception: Failed to set file group to 'users' for '/srv/dev-disk-by-uuid-7F9B-F0BC/backups/': Unknown error in /usr/share/openmediavault/engined/rpc/sharemgmt.inc:411

Stack trace:

#0 [internal function]: Engined\Rpc\ShareMgmt->set()

#1 /usr/share/php/openmediavault/rpc/serviceabstract.inc(124): call_user_func_array()

#2 /usr/share/php/openmediavault/rpc/rpc.inc(86): OMV\Rpc\ServiceAbstract->callMethod()

#3 /usr/sbin/omv-engined(544): OMV\Rpc\Rpc::call()

#4 {main}

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Thanks. Thought as much. its exFat and the GUi could be a bit more informative or just refuse to use this.