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Specifically the accessibility of hidden fields changed as they are not provided for the DOM anymore. This may have an impact on custom javascript code.
Please check if your custom javascript code it is still working for you.

Sometimes if you have problems with accessing hidden fields the following feature setting will help your use case:
You can add all fields there where you would need to be able to access them although they are hidden.

If you need to access hidden fields with your javascript you can add them to the feature setting and use the function:

adv.getValue(<itemId>, <fieldname>);

The Feature Setting can be set up like this:

If you need to access hidden fields with your javascript via DOM e.g. as a change handler there are two options you could perform in order to fix your custom javascript code:

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