Stephen
Assuming nothing else has changed the problem is most likely to be a fault with the pair from the exchange. you might have a dry join and earth or battery fault or even a partial short. The engineer will often want to do the simplest thing to complete the job and move onto the next job to keep his targets. However a lift and shift they will swap part or all of the line from exchange to house with a fresh pair. Usually the re-making of joints is the main fix. We will always insist on a lift and shift for a recurring broadband fault that doesnt point to local cabling, equipment or filters.
Because you loose the line on an incoming call this is always filters or cabling IME. You might want to swap the filters and make sure you have one on every phone in the house.
HTH,
ACW.