Studio version:

I have had some complicated masking and I have tried everything with the magic mask. I finally came across a trick that seems to work with 19.4.

• Mark out what you want to keep at the beginning.
• watch carefully as it masks it out
• stop it from masking as soon as you catch something off
• add more marks., you can even go back frames
• press the forward masking button.

No more going frame by frame. It’ll probably change randomly, but it might help in the short term.