What's causing the screens on my players to flash?

I've got several players running pcp, and my lms also runs on pcp. All works beautifully. However, I also have 3 hardware players - a boom, a transporter and a SB3 classic. So, the odd thing. Every couple of minutes, on all of the players, I get some text flash on the screens at full brightness. It's only on the screen for a fraction of a second so I can't read it. It might be the click to continue setup... Not sure though.

Any ideas?

Pete s