smbd / btrfs-Transaction high load on cpu - Bug while Backup Job WIndows 10

Problem startet in February 2018 (Where my last Update was made- but it should be daily)

I recognized  the process failed after watching for something else in the windows report, and because of the old backup files.

Readynas 

- FW: 6.9.3

- dust freed

Data Volume:

- 4 x 1 TB WD Red something which is to use with this NAS . i checked tripple

- XRAID

- data 1,39 TB

- Snapshots: 516.28 GB

- Free Space: 838.51 GB

- Total ~ 2,73 TB

- Type: Raid 5

-TRIED STUFF-

* switch off Bit-Rot from every share

* defrag

* delete snapshots

* switch samba protocols (smb 2 /3 ) ((installed samba plus for that)

* scrubing

* new users

* iperf (works great)

* write I/O internal 54 MB/s

* write from Network 29 MB/s

* read  from Network 55MB/s

-> wbadmin backup stream ~ 240 GB

Trying at the moment:

* balancing

process which takes 100% load "brtfs-transacti "

why a transaction on the file system stopps the whole samba process by sucking away the power ?

-> Priority?

Hope I could feed you with Infos.

PC:

Intel i5 somewhat 

Network works great to other devices

The SambaProcess slows and fastens by occupied and free cpu % power

Can someone stabilize this **bleep** ?

-> Controlling Application Consumption

Sorry I am an intermediate linux user / advanced windows user - but when you use a Marvel ARM Board with 1,2 GHz then optimize it. Every process going wild at that thing.