Can’t Control Volume on CarPlay

I can’t find any topics belong to CarPlay, so I’m asking this on iPhone topic.

I recently purchased a wireless CarPlay capable head unit. I’m having a great experience except for one thing: I can’t seem to control volume (especially on now playing song) beside from the volume buttons on the head unit.

It’s from brand named “Orca” rather than famous brands in audio, and here’s the thing: the volume buttons rather unresponsive at times and placed on the far side of my driving seat.

I read a couple of discussions here and articles elsewhere and can’t decide whether the disabled volume controls is a bug or feature for distractedless driving. I also can pause, change to prev & next songs from my iPhone so I think it’s rather pointless for a feature, isn’t it?

All I know is the volume control on my iPhone when connected to the CarPlay is showing “localhost” rather than a specific name like my AirPods or Homepod. I also have tried to reboot both devices and reconnect them but none of this solved the issue. I foolishly bought a bluetooth steering wheel remote control which has to be connected to my iPhone, so it also only functional for playback control, not as volume controls.

I appreciate if anyone can shed more info about this, Thank You.

iPhone XR

iOS 15.2.1

Orca ADR-9988 Pro+ Plus