There is a bug with the calculated TAB name in a TAB included inside another TAB. The horizontal space needed to show the text is calculated wrong when switching TAB in the master TAB, and back.
See included file to show the bug. Only in Web Direct. USER: admin PSWD: 12345
Filemaker server 18.104.22.168 on iMac High Sierra 10.13.6
Added: If text on active TAB is set to be in BOLD, is also a issue.