After market stereo battery drain

Please help!!!!!

I bought an xtrons stereo double din to replace my stream stereo, it has sat nav, dab etc and also has a can bus box so I can see engine temp/door open etc on the screen.

When fitted with the loom provided I get a slow battery drain. The stereo comes on only when you turn the key to the first click or when you start it, and turns itself off when when ignition off.

I am told it can't be the canbus gateway as that doesn't affect after market stereos so what could be causing the power drain?

Could it be that the can bus box is taking power from the canbus rather than the permanent live (yellow)

I'm so confused by it all, cheers