Diagnosis
The j9+ has a raised front bumper, but its rear end, where the Clean Base dock is, is taller. It's driving under an obstacle fine but then its rear hump is catching on the way out.
How to Fix It
Use Keep Out Zones in the app. After you have a smart map, go into the map editor, select "Keep Out Zones," and draw a zone covering the area under the chairs or the lip of the cabinet. The robot will avoid that entire virtual square during future cleanings.
If That Didn't Work
For a more permanent fix, you can adjust the robot's behavior. In the app, go to your robot's settings, then "Navigation," and toggle on "Careful Drive." This makes it more cautious around furniture, though it will slightly increase cleaning time.
Heads Up
The Keep Out Zones only work if the robot is cleaning using the smart map. If you just hit the "Clean" button on the robot itself, it will revert to a random clean and ignore all your zones, guaranteeing it'll get stuck again.