If a blue node is connected to another node and activated, and then is deleted, the connected node remains transparent on the testing screen. If the level is then completed by passing a packet through that node, a “solution is invalid” error results.
If the solution would be valid but take a different amount of time, there is a “Declared duration does not match simulated duration” error instead.
This is a known issue; it’s being tracked in our system. The problem here is that the client should be uninverting the linked node when the flipflop is deleted. In our system model, there should be no way for a node to be inverted without being attached to a flipflop, which is why the error is occurring.