My setup: Raspberry 4 / Raspberry OS; additional 3TB WD HDD attached via USB3

I was using hdparm to spin down this harddisk after 3o min. 
This **was working perfectly fine** until few days ago. 

Now, there was a power outage that caused the raspi to reboot, and since then the hdparm command just stopped working. 

Here is the output: 
```
root@raspi:/ # hdparm -S /dev/sdb
 -S: bad/missing standby-interval value (0..255)
	
root@raspi:/ # hdparm -S 36 /dev/sdb
/dev/sdb:
 setting standby to 36 (3 minutes)
 
root@sraspi:/ # hdparm -S /dev/sdb
 -S: bad/missing standby-interval value (0..255)
```
The drive is not spinning down after 3 min. 

Smartmontools say the disk is healthy, also some samba shares on the disk work fine. 
And like I said, before the power outage and forced reboot all was ok. 

Anybody has an idea what's the problem here???