The Ultimate Guide to solve your Roomba Error Codes - SafeMode Wiki
Fixing Roomba Error 9 and Circle Dance - YouTube
iRobot Roomba i7 Troubleshooting - iFixit
Roomba j7+ I have just gotten error 30 this morning and worked fine then at 9PM it's happened 3 times and I've emptied the bin, cleaned the sensors. 90Seconds later it appeared.
IROBOT Roomba S9 secret codes and hidden features - HardReset.info