I've been having this exact same problem, the dreaded IPC6023 error, and have contacted BT many times. They have been awful, passing me off to another dept and then closing the complaint. I open a new complaint and we start again, they sent out an engineer who did nothing and told me he thought he'd fixed it, he hadnt. I'm now waiting for the TC tech team to contact me, in the meantime I will send BT this link. Why on earth they they know about this problem when it happened to others already. Anyway, I'm so pleased I found your complaint and solution.