What Pat said is correct. The context that is being used to pre-populate data is the parent row from which the drawer is opened, rather than the specific rows inside the drawer. This is one of those edge case scenarios where “context” gets very tricky.
At this point I believe there are two options.
1. Move the table outside the drawer and run the mass action there.
2. Make the action a Row Action. Single row action buttons ovewrite the context in memory, whereas multiple row actions create a new object called “context rows” but don’t necessarily overrwite the single “context row”.
Again context is a complex area.
