Connection working only with scope connected

Hi,

I'm working on a traffic light simulation with Simulink [Version 8.0(r2012b)] / SimEvents. Today I've discovered a strange behavior of my model.

the red marked link (see picture) was connected to a scope for testing. (With a Vector Concatenate and Event to Time block, to get more scopes in one.)

at the end I removed the scope and suddenly the model wasn't working anymore

The "tr" subsystem input is connected to a "wvc" port of an SimEvents Signal Latch.

What am I missing?

br Bernhard