Android M8-S box - which company sold it, can you link to their product page to see if we can tell more from it
The "Kodi" box - same again, make, model and supplier might help us to think what could cause this different behaviour.
In case it helps and you've not see it before, you can adjust volume levels within Kodi without using the remote control volume buttons... With a video playing click the little speaker icon that appears when the playback controls are on screen. The sliders can be adjusted, and set as default for future playback if you find a good level.