Help with sandbox app filling an order from a different account that created the order



I’m investigating the code docs and playing around with the dev sandbox (setup at codesandbox I loaded the app in Kovan and was able to get the app to dispense ETH and ZRX (verified on and create WETH. I was also able to sign a “Create” and “Fill” order from the same account. However, if I sign a “Create” order with one account, I cannot Fill that order with another different account. There is an error: “Error: VM execution error.”

From my understanding of the code, it should be possible to do this. Am I wrong? Is there a bug or am I using this incorrectly?