I would like to chime in that we have had many of the same issues on our tenant with our Teams rooms. We had several room devices fail to upgrade properly. Several units have new meeting and join issues. This last week we struggled through "cannot fetch calendar" issues that affected all our room devices. Engaging Microsoft support through the O365 has been a thoroughly frustrating experience. The reps we work with have no training on these devices and have no power to fix these issues. I'm always waiting on technical leads for more information. Took two weeks to fix one issue which was mysteriously fixed with an account "background sync" of the affected accounts. The current Exchange online calendar issue was fixed mysteriously over the weekend without even a hint of issue listed on the 365 service health portal.
We love our MTR units and using Teams rooms. But as of late, I can not recommend the product to other companies if I'm asked. It has been too unstable and the support has been horribly lacking. Our hope is that things will improve quickly before our company deployment completes and our users are soured on the MTR product and start begging for Zoom rooms.