Could you share a link to your Shortlist story map so we can have a look at the issue? Or if the app is not one you want to make public can you share a link to the ArcGIS web map it displays?
There used to be a bug in the Shortlist where a tab wouldn't adopt the highlight color if it had a & character in its name. We fixed that some time ago though and I can't repro the issue with these two test maps using the latest version:
Shortlist with 5 tabs two of which has & character in it:
http://storymaps.esri.com/templates/shortlist/?webmap=7e2b602d8b054b8b8e7ca3756a9a75a8&DETAILS_PANEL...
Shortlist with 5 tabs:
http://storymaps.esri.com/templates/shortlist/?webmap=0856d82fb5fb4ae7adb787d4c2f5f0e3&DETAILS_PANEL...