I am seeing the same behavior on v1.05. This happened to me in two different styles.
It is not immediately obvious that any changes made in the Log Designer take effect immediately, and do not require a "save" operation. So I was editing a style, and not knowing how else to make it permanent, I did a "Save As" to the same style name. Viola, now I have two of every field.
I see that when a field is deleted in Log Designer, it is not deleted from the LogStyles table, but the LogBook and LogEditor fields are set to zero. In the F operation in SetStyles.php, if count>0 an update is performed on all records matching the IDValue and Name. This brings these deleted fields back from the dead, and joins them at the hip. Thus if there was some Save As goof as above, SetStyles.php does not catch it.
Hope this helps,