Minimum speed guarantees are nothing more than administrative, a point at which you can’t complain about speed , no one physically limits downloads to the MSG , the line delivers what it is capable of delivering irrespective of the MSG upto the speed profile you pay for , the Openreach service and the provider MSG are not linked in any real way as far as limiting the speed but what Openreach deliver is the basis for the MSG ….., the advertising authority and Ofcom requires the customer to be given this figure , unfortunately as is the way with unintended consequences, if the MSG is based on a faulty lines actual performance so artificially lower than if the line is fault free , then getting a speed issue resolved is problematic if it’s still delivering above the MSG .
The only ‘locking’ is if Openreach apply a banded profile to stop instability, normally FTTC uses dynamic bandwidth allocation, if a line gets worse , the speed reduces to keep it stable , if the line conditions improve (because a fault is removed) it gets better , but if the line were up one minute and down the next , DLM may effectively set the line semi permanently at a speed that’s stable , this is called banding and should release after a period if stability, but occasionally it needs to be requested to have it removed and to let the line retrain to it’s optimal speed.
Have you done as requested, router in the master socket test port and recheck, and run a line test yourself from your online account ?
