Hi @BasWep,
I hope you are doing well!
Firstly, have you made any modifications to the example? If so, could you share them?
A Factory Reset may not erase all the memory as the application itself must remain saved. FR clears the stack and application data, and it should be enough to clean the application and start a new network.
Can you confirm that you are enabling Permit Join on the Router in between your Control Bridge and your Light? This can be done by using the ZGWUI and according to the Zigbee 3 IoT Control Bridge App Note (KW41Z SDK/docs/wireless/Zigbee/Application Notes), Section 4.2.4 Joining Nodes to the Network.
Best regards, Julián