This is weird then, I didn't use MS210, I have MS225 in production and a few others, but never had this one happening. You could always set up one port in a classic way instead of aggregating them, then you should be 100% sure that there will be nothing happening. Also, if you lost the config, didn't the ports revert to trunk with native vlan 1 as the default setting? Wouldn't that keep your setup running? Meraki switches detect if there is LACP running on the other side and enable that if needed automatically. The dedicated vlan for management is best practice, to separate the management traffic from other production stuff, security reasons and many more.
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