The issue in Firefox is document caching. Firefox has a setting in the about:config that checks for documents that are cached. Here are steps on how to fix it:
- Type into the address bar: about:config
- Type into the Search: browser.cache.check_doc_frequency
- double click on the browser.cache.check_doc_frequency line to edit it
- change the value to: 1
- press OK to save.
3 is check only if it is outdated.
1 is always check.