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I search the community and did not see this issue listed, so I apologize if it already is. The issue that is occurring is when you search for email. Once you type what you're searching for and hit enter, it displays like it should, but if you click on a different folder, the search criteria disappears, but is still active in the background, so you can't click the X to remove the search criteria , as it's gone, but all folders show empty unless it has something to match the search criteria. The only way to clear the issue is logout and log back in. This is occurring on Firefox v56.0 on Windows 7 and on Chrome, not sure of the current version, but it's recent.
Unfortunately, I have lost a client to G Suite because of the issues in v 16 and have been threatened from others to change to another service. I hope updates keep coming out.