I have a problem with an old 770 where when the Roomba is docked the PSU light will flash intermittently (approximately once per second) and the light on the dock will flash then dim off at the same rate. I'm curious because this won't happen when the PSU is plugged directly into the Roomba, and will only happen after the Roomba has been fully charged so when it is sent out it cant find its way back. when this is happening and the Roomba is in the dock the battery charging light still fades in and out, but the "spot" and "dock" buttons will flash slightly after the PSU, the Roomba will also take a very long time to fully charge when this happens. So I guess I was wondering if there is anything I can do to fix this. (also the spinny sweeper underneath tends to stop and reverse as if something was tangled in it when just working on my carpet)