Use WaitSignal Task with cascaded layers

Hi everyone,
My situation that 1 Work Process to create different kinds of product and then feed to suitable work process(s)
I tried to make Works Process #1 to produce Product 100 based on the High status of a customised signal (StartProducing) until StartProducing goes Low, then Works Process #1 will produce Product 101.
But it doesn’t work properly. Works Process #1 produce 100 and then 101 and 100, then 101,… I used Python to print the status of StartProducing, which is functioning OK.
I have configured tasks in Works Process #1 as follow:
WaitSignal:Works Process #2:StartProducing:True?False:False

Create:100:
Feed::shelf:::True:True:
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WaitSignal:Works Process #7:StartProducing:True?False:False

Create:101:
Feed::shelf:::True:True:
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Delay:3
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Please help me out with this.
Thank you in advanced!