Robot Reviews

Hi all. I've got two Scooba robots - one a model 340 and the other a 390. Both seem to be exhibiting the same issue with their bumpers, in that the sensors do not seem to be reliably reacting when the bot collides with an object. Sometimes they react exactly like they should - the bot stops, turns off it's brush and pump motors, backs up slightly, spins to a new direction, then turns the pump and brush motors back on. Sometimes the bot acts like it didn't collide with anything and will continue trying to drive itself into the wall or object for a few seconds, often sliding sideways if the bot collided at an angle. They also seem to do an escape spins fairly often. On very rare occasion, I'll get the “uh-oh” sound with 3 beeps, which I know is a bumper error. I have a copy of the Scooba service manual, and I've followed it's recommendations - the bumper does seem to be moving freely, there are no debris that I can visually see, and I've blown out the bumper with compressed air. I've also run through the Built-in Test, and BiT #2 completes successfully every time I've tried it. Pressing on the left or right sides of the bumper will immediately illuminate the corresponding light. I do notice that I do have to press harder than I'd expect on the front center of the bumper to get it to register, however. I've seen suggestions that this sort of issue could be a mechanical movement issue, however visually everything looks like I'd expect it to, and I don't see anything obviously binding when I mechanically manipulate the bumper.

Any suggestions for things to try or specific areas to inspect?