This is an update to my earlier post. I had continual error code 2 of tangled brushes that stopped my 880 series every 10 minutes. But they are EXTREMELY clean. But I replaced them OEM brushes, an entirely new brush roller assembly from iRobot at their suggestion. I installed and thoroughly cleaned the machine. Started Roomba up…….same error code. So I bought a new battery pack, a Lithium Ion, non Roomba manufacturer, but had good ratings. SUCCESS!! The new battery solved the error code 2 tangled brushes and I probably wasted money on new rollers and roller brush assembly as well as wasting a significant amount of time doing extensive disassembly that required only a new battery pack. The lithium battery is much lighter which allows the Roomba to climb on board atop thicker rugs much easier and it runs for a at least 2 + hours before heading back to base for recharge, even though battery indicator is still green. I recommend make sure brushes are clean and the front wheel spinner is free to swivel. Then buy a new battery that fits your series of machine. Charge the battery fully. Do a reset of your Roomba. Then turn it loose for tangle 2 error free cleaning once again! The disassembly and extensive cleaning as well as new new parts did not solve anything. Only the NEW Battery fixed it for me.