Here are some ideas/thoughts:
1: If possible check the bandwidth (input/output) report for days that problems had been reported. In some cases, a high volume of uploads can actually cause network issues. Most of the time, upload speeds are smaller than download speeds, therefore upload speeds are causing a bottleneck.
Use utilization graphs to see if peak times correlate to incidents.
2: If your equipment has QoS capabilities, implement QoS for Microsoft Teams:
https://learn.microsoft.com/en-us/microsoftteams/qos-in-teams
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