I am not sure which UI your tracking window came from, but the FetishNightFall tracking window uses widgets02.dds and the sourcerect for that is a circle. It implies \images\widgets02.dds which does not reside in the FetishNightFall\Images directory. Therefore, it gets it from Default\images directory.
The Default\images\widgets01.dds does return that wierd symbol from the same sourcerect.
If you have a version of widget01.dds distributed with your UI mod that is intended to override the default it should reside in your UI's \images directory. If not found there, the UI will load it from the Default\images directory.
The attached code snippet may help to get your tracking window back in shape.
Code:
<ImageStyle Filter="true" Name="Unchecked">
<ImageFrame Name="image" Source="images/widgets02.dds" SourceRect="192,215,204,227" />
</ImageStyle>
<ImageStyle Filter="true" Name="Checked">
<ImageFrame Name="image" Source="images/widgets02.dds" SourceRect="168,214,180,226" />
</ImageStyle>
Hope this helps.