Custom components are forms with their own components and are seen by the main form as one single component. The main form doesn’t see the code inside the custom component and the custom component doesn’t see the content of the main form.
If you want a custom component to tell the main form that something is happening inside the custom component, then you need to define an event. A real (custom) component event, not an x-... custom event managed with add_event_handler.
If you want the main form to expose something to a custom component, you need to create a property on the custom component and set that property from the form (or in some cases the IDE), so the custom component can work with its own properties.
If you are having problems across “components” rather than across “custom components”, then you may need to use custom events, named x-... and managed with add_event_handler.
Well… maybe yes, but I don’t see your code.
I could have a look at it if you share a clone link.
Please pay attention to the formatting on your posts. Python code without indentation is difficult to read. Here are a few tips: How to ask a good question