[marko-mb]

The Minix U9H has this issue, as has every no-name AMLogic device I've used, and it's very annoying - particularly as the Minix U9H has well implemented remote control power on and off functionality (allowing you to power it up from 'shutdown' via the remote control).  Even when 'off' the Minix U9H stops other devices properly using CEC.    

There has been progress fixing U-Boot on closed source Android AML devices as detailed in THIS thread (click) and HERE (click) in this CoreELEC Wiki

AML devices like the ODROID C2, Khadas VIM, Le Potato and I expect the Vero 4K have open source U-Boot code that can and has be modified.

---

EDIT: started doing some HDMI CEC testing with my old HiSense 4K TV and a Yamaha AVR.
Going to see what blocks HDMI-CEC...
Results:

Apple TV 4K = Good, in fact it's reasonably speedy. Shuts down and wakes up both the TV and AVR after Sleeping using the Menu button.
Vero 4K = Good, it does not Jam other devices HDMI CEC commands when in Suspend mode 

Can the CEC problem be solved with u boot and how? I cannot find any info online...