Hi, no idea why, sounds bad.

• Repair System Registry and Files

Find the Dos Prompt Right or Powershell Click and Run as Administrator then : Copy/Paste to Dos Window : SFC /Scannow (SFC <space>/Scannow) then hit Enter. Reboot when completed.

Please uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 59.0.1 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

Please let us know if this solved your issue or if need further assistance.

The Dos scan turned up fine, no issues. I did the uninstall, could not find the files, so they might have deleted themselves when I uninstalled. The Disk Cleanup, even though I have never run it before, only gave me a couple hundred megabytes of space, a little over 600 at most. I reinstalled firefox (I was using the most up to date before) and it reloads my tabs, and again, the wrong ones load. Of the 20+ tabs, this time 3 of them have been overwritten.

It sounds that Firefox used an older copy of recovery.jsonlz4 to create sessionstore.jsonlz4 that didn't include the latest changes.

Are you closing Firefox immediately after closing some tabs?

You can also use this startup setting as this is more reliable than the others.

• "Show my windows and tabs from last time"

I have been using "Show my windows and tabs from last time" as I have not tried using the save session system. The tabs that get overwritten are not even being overwritten by the most recently closed tabs, its tabs from a while back that were closed. The overwritten tabs have the same site icon as the site I had open before I closed it, but the name has changed to what it got overwritten by. They are also spread around the tab list, so they arent the most recently opened ones, they are spread randomly among the tabs, not seeming to have a pattern.

Why is Firefox so unpredictable in recalling browsers and tabs from the last session? This unpredictability has become standard for the last several versions. Why is that?

As user LokiDogfish reports, the browser and tabs that are recalled are arbitrarily called up from sessions that may have even been weeks ago. I am cold booting my machine and when I reopen Firefox it is hit or miss whether it will load the last session (it is actually rare anymore that it will do this). Sometimes if I save a bookmark of all tabs, it will reopen those, other times it just recalls a browser session from a week or two, or even a month before. And then it may repeatedly recall that browser session until a new bookmark of tabs is created. Unfortunately, this as much information that I am able to discern over the behavior and what may prompt Firefox's erratic session recall.

Hi Steven P Mitchell, Firefox should be updating a file named recovery.jsonlz4 throughout your session with changes to what is displayed in your tabs, as often as every 15 seconds.

You might check before shutting down after a long session whether your recovery.jsonlz4 file is way behind on updates. To try that:

You can open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" Help > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, click the "Open Folder" (or "Show in Finder") button.

In your profile folder, double-click into the sessionstore-backups folder. The kinds of files you may find among your sessionstore files are:

• recovery.jsonlz4: the windows and tabs in your currently live Firefox session (or, if Firefox crashed at the last shutdown and is still closed, your last session)
• recovery.baklz4: a backup copy of recovery.jsonlz4
• previous.jsonlz4: the windows and tabs in your last Firefox session
• upgrade.jsonlz4-build_id: the windows and tabs in the Firefox session that was live at the time of your last update
• various .js files from Firefox 55 or earlier

recovery.baklz4 usually is a copy of recovery.jsonlz4 from just before the latest update.

Does it seem that these files are updating normally?

At shutdown (assuming no crash during shutdown), Firefox should create a file named sessionstore.jsonlz4 at the main level of the profile folder, and delete recovery.jsonlz4 and recovery.baklz4 from the sessionstore-backups folder.

At your next Firefox startup, sessionstore.jsonlz4 should be removed.

While Firefox is still running, could you check your profile folder, main level, to confirm that there is no sessionstore.jsonlz4 file there? If there is, perhaps it is locked or read only for some reason and cannot be replaced. That could explain some problems.

You might also consider using an extension like the following as a fallback in case Firefox's built-in session restore feature does not work correctly. It maintains a separate data file.

https://addons.mozilla.org/firefox/addon/tab-session-manager/