Header Anomaly With Wiki Alias "dtc"

Create a new wiki with identifier of "dtc" (without quotes).

Header pages will display an anomaly under the "Edit"/"More actions" buttons displaying "Annotations" with a background of small icons.

Sorry I'm new to version 7 having last used version 5.1 so not sure if this "Annotations" menu is supposed to be there but it isn't there on other wikis created and the graphical icon background definitely looks wrong. I use "dtc" as the identifier because it is my company domain name.

If the wiki alias is changed to "xxx" or "dtc1" then the anomaly goes away. Similarly, if the alias is changed to something else, and the page is accessed using the original "dtc" in the URL rather than the alias, then the header is again displayed correctly. i.e., only seems to be a problem if wiki alias is "dtc".