I don't know based on the rulebook.

The provided context does not specify what happens if multiple Investigators attempt to escape via the same Objective in the same round but only some succeed, nor does it clarify whether the remaining Investigators get another chance to escape in a later round or are left behind. The rules on page 15 state that "Any Investigators who have not escaped and are still on the board after the final round count as being killed," but do not address partial escapes within a round or restrictions on subsequent escape attempts.

To answer this question definitively, the rulebook would need to clarify:

• Whether the escape Objective can be used multiple times or by multiple Investigators in different rounds.
• If there are any restrictions on attempting to escape after a failed or partial group escape.

Source: page 15.

Source: Core Rules (pp. 15, 16, 2, 6, 7)