How can I investigate what is killing my router. I will like to know if is a bad device or some bad rule.
About the only way is by clicking the checkbox next to any app, rule, or device you aren't absolutely positive about. Sometimes mis-configured rules or possibly device code can cause issues.
Your hub's "Logs" (past logs) are a great starting point when troubleshooting issues:
Also check this document out if you need further assistance from community or if you need to reach out to support:
thanks for tip