I believe you can start by checking one of these documents.
https://documentation.meraki.com/MR/Wi-Fi_Basics_and_Best_Practices
But if you could share some of the settings, it would be good to try to make a more precise assessment, for example, how is the minimum bitrate configured? What type of authentication are you using?
Does the problem occur on both 2.4 and 5Ghz frequencies?
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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