To be honest, it's not that easy to troubleshoot.
That example you gave is an example of something very generic, and the SNR can be low for several reasons, such as coverage problems, signal obstruction, signal absorption, or even the client's WiFi card is not so good.
I hope the link below can help.
Tools and Troubleshooting - Cisco Meraki Documentation
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
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