Not had any issues with using MS Teams with MR42's or any other Meraki MR's. The issues that you have can they be replicated everytime or is it a random error. I cannot see how MS Teams would have that effect on the Meraki MR
@DarNic unless you really need it, always disable client load balancing as some clients really don't behave well with it enabled. I'd also make SSIDs either 2.4GHz or 5GHz as opposed to both if you are having issues as this can help.