Additional info from reporter:
Mattermost-Version: 4.9.2
Database-Version: 4.9.0
Database: mysql
Server OS: Debian GNU/Linux 8
My Desktop OS: macOS (High Sierra)
My mobile OS: iOS 11.4
But client versions vary much in our team. Have lot's of Android users plus Desktop Browser-only users. Windows 7 perhaps, don't know.