Web Security -> HTTP/S -> URL Filtering
If you click one of the "allow/block content that does not match the criteria below." or the "Block URLs with a reputation below a threshold of:" the page reloads so that any other changes on the same page that have not been saved will be cleared.
I expect this is not specific to the beta, but also in older versions. In stead of making a "fix" you can just write a warning - e.g.:
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Block URLs with a reputation below a threshold of:
(This setting will reload the page, so please apply any unsaved settings):
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