AidanP: Before I got the 17a profile the day before I had tried shorting out the dsl cable by exposing the 2 wires from an old dsl cable plugging it into the modem and the master splitter then waited for a connection then shorted them which did nothing exept limit our download speed to 10 mbps for a short period but the next day I found out that we were put to the 17a profile, I don't know if this was related to me shorting the cable.
often changes to the cabling can trigger port changes.
99% of the time, when i plug in my 7390 i jump straight to 17a, other times it happens is while line faults are being repaired.
I've always put the 7390 down to a logic choice by AVM pushing towards 17a rather than 8b for profile (it is a negotiation with ddDLM rather than a set profile as with DLM) - as mentioned previously in this thread, forcing this can cause very unwanted actions, I've physically broken my port twice.