Crowd proximity trigger problem

[chrisdisco]

Hello all, I'm struggling with a crowd setup...

The goal is to stop the first agents when they reach the box, then stop the agents behind them when they are close enough to other stopped agents. So the stopping ripples outwards in an infection type way

CROWD TRIGGER 1

The first crowd trigger stops agents when they reach the box and adds them to the "ObjStopped" group, removing them from the "Walking" group.

CROWD TRIGGER 2 (problem) 

I think that, once they are removed form the "Walking" group they should no longer be ignored by the "ignore same group" checkbox in the second, particle proximity, trigger and therefore agents in the "walking" group that are clsose enough should be 'triggered' and also stopped. I feel sure that this should work but it does not.

I know the trigger itself works because if I untick "ignore same group" all the agents will trigger into stopping imediately. 

I can also see in the spreadsheet that agents stopped by the first, bounding box, trigger do leave the walking group

Any help, greatly appreciated. Scene file attached

CrowdTest_03.hipnc