Linx Devices are no good / Ring Group Issues

We have had this “system” installed for about 2 months now, there are 2 base stations and 7 Linx devices.

We have a ring group that is setup to ring 6 lines. It often only rings some of the extensions (not any specific ones) and once we answer the phone it is very common for us to lose the call. When we speak to the client after calling them back, they tell us that they were, “transferred to the fax line” almost every time.

The farthest Linx device is maybe 20 feet away and the 2 base stations are about 30 feet from each other. Two Linx devices have been replaced and one base station has been replaced.

Our connection is a 60Meg down connection and our router is a TP-LINK TL-WDR3600 running DD-WRT firmware. QOS is enabled and dedicating 10Mb to each of the base stations via their MAC addresses.

Any help is appreciated.

Update-

This morning I turned off the ring group and had the main number ring each extension individually. Every extension worked when trying this. Once I turned the ring group back on, only some of the extensions would ring.

Not sure if someone else has some more insight for me.