We haven't introduced any significant changes in the simulator to cause such a delay and we haven't received any similar reports as well. This is why I want to ask you if you can elaborate a bit more on the environment in which you can reproduce the reported delay. It would help us to know in which AppBuilder client you're running the Simulator. Also, would you mind sharing with us your project? You can start a support ticket and attach it there or if you're working with the Windows or InBrowser clients of AppBuilder, if you share the name of your solution we can try to open it from the cloud. If you'd rather keep your project information private then I would strongly encourage you to share the information about it in a support ticket and we will only update this forum thread to let the community know the results of any further investigation.
Regarding the "Applicaiton Error"
you reported, we've actually received similar reports before. There are a few threads you can check out for further information on the possible causes and solutions for the issue:
Also looking at the two issues together, the only thing that comes to mind as a possible cause for both is a slow internet connection on your side. However without further information about the environment in which the simulator delay comes up and a solution we can test locally, I cannot suggest anything specific.
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