N_Cook wrote:
I'd like to eliminate a problem of syncing between pc and projector
firstly.

What was the connection to the PC - VGA, HDMI, other? VGA has separate
sync signals, and an intermittent cable or connector might cause
something like this. People often bend the last few inches of a VGA
cable quite a lot, if (for example) the connector is on the right side
of their laptop but the cable needs to run off to the left. Sometimes
they will set their laptop on top of the cable, which might cause
intermittents to show up if they use the keyboard or trackpad during
the presentation.

If the projector was on the ceiling, with a cable routed through the
ceiling and wall to a socket on the wall, maybe that cable is going
intermittent.

Matt Roberds