IPtouch no display

[mopo]

Hi Guys,
I just put some iptouch (4018's) on site connected to a netgear poe switch.

Users are complaining because the display's are coming up blank sometimes (phone still works).
I tried adjusting contrast but this wasn't the issue, pulled the network from the rear and back in and it came back up and worked.

Any ideas? I thought maybe low voltage due to crappy wiring?

Cheers
P