So I installed 2 CS KXTDA0141ce on the customers KXTDA100. They are using 4 KXTCA275UK phones & everyone is happy. I should have upgraded the FW it is still on R2 but it was a long day. Everything works very well for 5 weeks now customer is saying that the range has dropped off & they are losing connection in places where it was previously good. I have checked both CS on the system & both are live. I know that each CS can only handle 2 calls simultaneously & as they are in different places call 3 may have problems being handled at the limit of range.But why does it work OK for 5 weeks & then performance drop off? Upgrading the FW will not improve coverage from the CS.