My Mac can't remember passwords, and suddenly forgets them?!

[EttVenter]

For some reason, safari seems to want to nuke SOME of its cookies from time to time. Especially when I restart the machine.

It doesn't nuke it ALL, though. But I keep having to sign in to a bunch of stuff and it's getting on my nerves. Sometimes I'll have a gmail tab and a Facebook tab amongst my open tabs, and all of a sudden those pages will seemingly "log out", and I'll have to sign in again.

Out of sheer desperation, I nuked my entire OS X installation last night, and on a fresh, clean, untarnished OS X installation, it's still doing this. Any ideas what the hell is going on?

2013 15" rMBP El Capitan.
Any ideas?

 

[Rodan52]

How did you "nuke" your OS and how did you restore your data? For example if you used the El Capitan installer went to Disk Utility and erased and reformatted the HD then performed an install you would have had an opportunity to restore your data during the process. If you did that then you have most likely reinstalled the problem.
You have proved it's not the Operating System at fault though.

If you are using Time Machine as your backup.
If you reinstall your OS don’t choose "Restore from Time Machine Backup". Make a simple install after you reformatted your drive with Disk Utility.

After the install the setup process will start and you can choose if you want to restore from Time Machine. I would recommend you to deselect the System to restore, just your home directory and your applications. So you will just restore your data (docs, music, pics), your applications settings (~/Libary) and the application bundles from /Application.

This the closest you can get to a "clean" install, without manually migrate your data and setup again every single app.