Light source inside may be overheating. Make sure the vents are not clogged with dust, or you have have to point a bigger fan at it.

I had the same issue, I opened mine up, disconnected and reconnected the keypad on the top panel. Now I the source button will allow me to choose HDMI. It may have been a loose wire.

I opened mine up, disconnected and reconnected the keypad on the top panel. Now I the source button will allow me to choose HDMI. It may have been a loose wire.

I have the same issues as Frances