troubleshoot and prevent multiple signal updates in one time step

I have run into a situation where a signal in a simulink model is occasionally being updated twice in one simulation time step. This causes my model output to as expected most of the time, but when this situation occurs, I get unexpected results.

Is there an easy (or methodical) way to trace why a signal get updated twice in a single time step?

Better yet, is there a best practices method to prevent this from occurring at all?