my brother went through the same issues starting this year since he started bowling competitively with me,
what worked for him was starting the ball out about chest level hand underneath the ball and wrist slighly broken (or cocked back)
then as he did his pushaway and dropped into his backswing I had him really focus on keeping his elbow to the inside (close to his body)
smooth swing and emphasis on the elbow tight to the body on the swing and really just focusing on an uncupped to cupped wrist movement and getting his thumb out of the ball before turning the hand
this really worked well for him, he had a complete spinner release and slower speed around 15-16mph and the ball would have an uncontrollable hook on the backend
since we started to change his swing and release his track is up around the correct area,
and his ball motion is so much improved some guys in the league cant believe it
his carry is a lot better and his speed and revolutions are up a lot also
he still has a lot of movement on the ball, but the movement is now controllable
things that really helped him were starting with the wrist uncocked when he started the ball
keeping the elbow in towards the body,
and getting the thumb out with the uncocked to cocked wrist motion