If you are losing the internet (e.g. the connection is regularly resyncing of its own accord), it would suggest you have a physical fault.
Such a fault could/does gradually diminish sync & therefore throughput speeds, possibly ending up with DLM putting you on a low speed capped/banded connection profile.
For anyone to comment in detail, you would need to monitor & post your connection stats for a few days to see what problems are developing.
However, the BT supplied modems (Huawei HG612 or ECI) are locked down as supplied, so only BT and your ISP can see connection stats.
The Huawei HG612 can be easily unlocked to provide all the stats you could wish for.
The ECI modem can also be unlocked (much more difficult) & currently the stats obtained aren't all that reliable.
Unlocking modems probably breaches BT's and ISPs' terms and conditions, but HG612 modems can be obtained quite regularly via ebay, allowing you to keep the original modem as supplied for when BT need to run tests using originally supplied equipment.
I have attached an example from a monitored connection that exhibited high errors from first installation.
DLM turned on Interleaving & the errors have now switched type & are being forward corrected (FEC).
The connection has indeed lost some sync speed, but it does now seem stable.
It will be monitored for a longer period, just in case a fault does still need to be reported.
Apparently that connection started at 60Mb throughput when first installed a while ago.
It is now in sync at just over 50Mb. i.e. a loss of 10Mb or so.
It is also a Plusnet connection.
