my discus pr is 136' 3" with a 2k , 20 years ago, so I am going to give you my advise and then let you read other more experienced opinions.
If the thumb was level at release, the flight of the discus was clean. If the thumb was tilted, (indicating the palm and other fingers are also tilted), then the flight wobbled. When I say "level", I released when my arm was parallel with my shoulder. The other basic technique and form is the "ideal" clockwise rotation of the release hand, leaving the inner side skin surface of the index finger last...all the fingers curl off at release and the discus having as its last skin contact on a callous or rough patch on the inner part of the index finger, built up from constant practice.