Problem with DECT telephony?

Question

Asterisk

Colleagues, we have Spectralink Dect Server 6500, Spectralink BS, Panasonic kx-tg8061ru radio tubes. The problem is that when you call, it's very phony, you can't even hear the voice. This situation arises both when making a call “in the local area” and to the world. BUT it is worth noting that once through time. Sometimes you even communicate (10-15 seconds) and it starts. Changed codecs, tubes, bs, does not help. Rules all Asterisk. The room is large, without neighbors with interference.
What could be the problem?
Thank you!