This is something that has been driving me crazy for a while. Whenever I adjust a mask path, the resolution of the preview window drops to 1/2 and displays the words "Adaptive Resolution (1/2)" appear in the top right corner of the preview window.
This make it really difficult to make precise adjustments. Is there a way to prevent resolution loss when adjusting mask paths? I've tried, to no avail, changing the Adaptive Resolution settings in the Preferences panel.
In the Composition Panel select OFF (final quality) under the fast preview options.