QNAP TS-109 energy consumption

Hi,

i've a QNAP TS-109 Pro II. It has a Marvell Feroceon 88f5182 [Orion-NAS] SoC (armel).
Currently I'm running Debian 10.7.

I am experiencing a problem with energy consumption.
With original QNAP firmware (3.3.3) my qnap always consumes ~14 Watt (also if hard disk was in standby state...).
Now the power consumption is really strange:

-power on qnap and debian starts (hdd active): 19 Watt permanent.
-put the hard disk in standby state (hdparm -y /dev/sda): 10 Watt permanent (good).
-hard disk wake up: 28 Watt permanent.
-put the hard disk in standby state: 19 Watt permanent.
-hard disk wake up: 10 Watt permanent.
-put the hard disk in standby state: 10 Watt permanent.
...

Tested on kernel: 4.9 , 4.19 , 5.4 , 5.9 , 5.11-rc2

Thanks a lot
Marco