Normally Firefox will show up to 50 addresses between back and forward history. But when you restore a previous session, it is truncated to no more than 10 addresses.

To check on or modify these settings:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste sess and pause while the list is filtered

(3) If the browser.sessionhistory.max_entries preference is bolded and "user set" to some value lower than 50, you can right-click > Reset it to restore the default value of 50 (or you can double-click it and enter your preferred value)

(4) If the browser.sessionstore.max_serialize_back preference is bolded and "user set" to some value lower than 10, you can right-click > Reset it to restore the default value of 10 (or you can double-click it and enter your preferred value)

I probably should mention two things which sometimes trip up users about that particular list:

(1) If at any point, you followed a link that opened in a new tab, the new tab only has the back-forward history back to that point, and you need to check the earlier tab for the rest of it.

(2) The back-forward history doesn't show pages you visited on detours, i.e., if you are on a search results page and look at the first result, and go back, and then look at the second result, the first result will not appear in the tab's back-forward history. (In that case, you can use the History sidebar or Library dialog to fill in the gaps.)

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button# or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button# or Tools -> Add-ons -> Appearance
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems