The VP4 station blinking red is a "Connection Timeout". This means that that the station is no longer receiving the heartbeat message from the core. The Heartbeat function of the VPage works in the following way:
1)The VPage sends a message to the Q-sys core to indicate that the station is online. If the message is recived by the core the Plug-in status bar turns green. But if is not, the status bar goes red.
2)When the core receives this message it then in return, it sends a message to the station to indicate that the core is online. if the station doesn't receive the message the led's start blinking red.
This processes happens every 6 seconds.
A network issue could also cause this behavior so here a few steps to find out if the issue is on the hardware or in the network:
1) Make sure that ll the stations are using Firmware V1.09 and Plug in Version 1.4
2) Perform a network scan to make sure that no other devices are using the IP adress of the stations.
3) Check that there are no duplicate IP addresses in the Q-sys file.
4) Connect the station to the same network switch that the core is connected to and see if it blinks red too (Make sure that there are no VLans or network isolation between the core and the Station)
5) Make sure that Dip Switch #1 and #2 are in the OFF position