seems like the nightmare I used to have.
I used to use DMT to watch bitswapping on my speedtouch 585v6 back in the days I was on ipstream, and a frequent event was bitswapping would run after I resynched but then after a random amount of time (usually anything from a few hours to a week) bitswapping would simply just stop working and then my crc errors would go through the roof.
The cause could be anything such as dodgy router firmware, dodgy dslam firmware, or something like the router not been fully compatible with the dslam.