User Claiming that their Teams Calendar is reverting back changes he is making

We have a particular user from close to 1000 users under our organisation that is claiming that the Teams Calendar changes he is doing are being reverted back to what they where before.

Is there a way I can track if this is true from the admin portal? This is not the first time the user claimed this and hence did not attend important meetings. It's important that the data we get is accurate as we might have to take steps against the user.

thanks.