If it's bumping more, the cliff sensors on the bottom or the front touch sensor are probably dirty. You'll want to wipe them down carefully.
First, turn the robot over. You'll see four cliff sensors—one near each corner on the bottom. Also, look for the charging contacts. Take a clean, dry cloth and gently wipe all the sensors and the metal charging contacts. Don't use any liquids.
Next, check the front castor wheel. Pull firmly on the wheel to remove it. Look inside the wheel cavity and clear out any hair or debris. Spin the wheel by hand. If it's sticky, you can remove the axle to get any wrapped hair out. Make sure it clicks back into place when you're done.
Do this sensor cleaning once a month. A clogged front wheel doesn't just cause navigation issues—it can actually damage your floors.