the PicoPix Max is designed as a simple-to-use portable projector. The way it chooses which input source to show is therefore also simple and automatic:
- the projector will automatically switch to the most recent cable that’s plugged in. No need to switch source manually.
- when you unplug a cable, the projector goes back to the source that was previously active.
- pressing [Home] always switches to the internal Android.
- from the Settings screen you can switch to another source manually.
So what’s likely happening in your case is that the HDMI device is periodically activating (for whatever reason), and then deactivating, but never sending an actual video signal.
The workaround at the moment is to unplug the cable.
I am tempted to say the external device is the problem (by periodically sending bogus activations). But we are monitoring this user-experience, and if many people complain, we will add an option to turn off this automatic-source-selection feature.