Post in direct support and have them check your line stats. They can also set a monitor on your line for a 24 hour period in lantern. Just in case they cant see an issue when you post.
There was a time where bell use to provide this information in their modems diagnostics page.
If your SNR (signal to noise ratio) is dropping below 6dbm and you start to get a high bit error rate in the form of CRC errors for a brief period of time it might explain what your experiencing.
With ADSL1 you should ideally have a SNR of 12 or higher to maintain perfect connectivity in all conditions.
I once had a similar issue when I was in high school after my parents moved to a new house.
The issue turned out to be with the inside wiring of my parents house that was causing the high bit error rate.
I disconnected a wire from my distribution bic block that ran in the middle of a large bundle of electrical wiring for about 45 feet as well as installed a makeshift pots splitter (2 filters daisy chained plugged in the demarc test port and a new cat6 run to my modem.)
Doing all that brought me from a 8DB SNR on my downstream to a 18DB SNR and dropped my attenuation as well.
edit: I forgot to mention if you switch from fastpath to interleave it will also reduce your bit error rate. But will increase your overall ping.
edit: Also if
Kovy is still around but he has been instrumental in assisting me in fixing many bell users problems when I worked at a computer store. (Customers use to call me after the Bell India support line couldn't help them)
Between him and DeadPool they have probably saved bell from rolling out a service tech for hundreds of people with issues.