When loading the content of tab, the loading indicator's position is not correct. For the kendo default theme, the indicator is at the top of tab header (correct). For the legacy theme (WebBlue), the indicator is at the bottom of tab header, besides, the width of that indicator is bigger than the width of the header.
I suggest you direct this report to our forums or support system on telerik.,com. Also have in mind that we provide limited support to legacy themes.