Where is my bottleneck?

With Boolean Toolbox , you should be able to force flow using the logic gates. I would think that simple AND formulas would be effective for stopping a flow until it’s synchronized, for example.

Actually…OR would suffice as you can set the gates to not continue until all inputs are set. Using AND, OR, XOR etc should be valuable for flow control and synchronization (haven’t tried specifically for that, but the option to wait for all inputs to be set would have that effect).