(C2121) ’else’ Transitions exiting from connector (‘else’ is alternative to transitions exiting the connector, not the source state)
The following 2 figures seem similar, but figure 2 may run into non-determinism. The 'else' transition checks negation of all other arrows exiting the same source, connector in this case, not negation of all transitions exiting the same source state. When execution is in state S1 and E2 is generated, figure 1 will transition to S5, whereas figure 2 will create non-determinism between S5 and S3 (the 'else' trigger evaluates to 'not E1').