Ok, so here is the scenario.
There is one out with runners at first and third bases.
The batter hits a fly ball to shallow right field. The runner at first base does not tag up and takes off for second base. The runner at third base waits. The right fielder makes a diving catch while the runner at third base tags up and crosses home plate before the right fielder throws to first base to get that runner out.
Would the third out be a force out since he did not tag up, thereby eliminating the run scored?