We still have the same issue with the ringing too.
Our phoneline is connected to the wall master socket installed back in 2000. We have had lots of issues in the past with the pavement chamber filling with water causing all sorts of problems with both telephone and broadband over the years, so wonder if it is something there causing issues this time.
If I call the landline from my mobile, I can hear the ringing on the mobile, but the landline misses the first ring, does the second ring, sometimes does part of the third ring but not always, then you might get another full ring. The handset just shows incoming call, no caller ID. If I do 1471 from the landline it tells me my mobile number I used to make the call.
I am on my second set of BT DECT phones - I replaced one set as they were quite old when the problem first occurred, but the issue remained so is something to do with the landline to the house.
Is it possible to get an engineer out to do some checks to save my sanity?
Keep a fire extinguisher handy !