The most common reasons:
You use non-working, unstable, low-quality proxies in ZennoPoster.
Insufficient waiting pauses for loading site elements.
For example, you don’t use proxy when debugging and try to start the project in ZennoPoster in the intended mode immediately. You shouldn’t rush to start the project with a proxy in ZennoPoster. You should observe how the project runs without a proxy; you may notice some problems in the algorithm and continue debugging the project. Take time to observe how the program runs in different modes of input settings. Maybe you need to supplement the project with dome checks, pauses and waiting for elements in particularly critical places. Then try to connect a proxy to the project.
As already mentioned in point 1, you may need to add pauses and waiting cycles for loading elements, because ProjectMaker debugging speed is much slower than in ZennoPoster due to animation. In this case, when debugging ProjectMaker, the project may work correctly due to delays in the animation, but an error may occur in ZennoPoster because the project runs faster without animation and the elements of the site do not have enough time lo load. You need to provide such problematic areas of the project with additional pauses waiting for loading elements.
Also in the Project Maker you can simulate the execution speed in the same way as in ZennoPoster by disabling the rendering of the project execution.