Repeated "Safari wants to use the 'Local Items' keychain" alert

I am getting this alert repeatedly. Sometimes but not always, it shows when I start Safari. Sometimes it shows when I quit Safari. It also comes up periodically in the Preview app. I'm not entirely sure how to reproduce it, but it happens a few times per day:

Whenever I see the alert, I enter my keychain password, which it seems to accept, but then the same alert will come up again some time later.

I read in this answer that deleting all files and folders in ~/Library/Keychains/ and rebooting might resolve it. I tried this, but I am still getting the prompt repeatedly. I also get it in Preview sometimes. Not sure why. I have entered my Keychain Access password successfully several times.

I contacted Apple Support about this by phone, and they guided me through "Resetting my default keychain" as per this button:

I did that, shut down my computer, turned it back on again, and I am still seeing the alert.

Apple support also guided me through changing my user password under users & groups.

I clicked "change password" and entered a new password.

This had no effect - I am still seeing the alert. I had to enter the new password in order to dismiss the alerts, but they kept coming back again as they did before.

Also, separately, when I go to Keychain Access to view a stored wi-fi password and click on the name of a network in the list from this screen:

And then check "show password":

I am prompted to enter my Mac OS User password as I expect:

I enter the password successfully, and then it shows the same prompt a second time. I enter the same password again, and then it shows another prompt saying that Mac OS wants to make changes to the System keychain and asks me for an administrator username and password with the username and password fields both blank:

I thought this was strange because the username "Mike Eng" from the earlier prompts is an administrator username. Not sure if that issue is related.

Mac OS 10.12.6

Mike, It sound like you've got login data for at least one web site stored in Safari, and the browser is having a hard time accessing it. Open up Safari Preferences and click on the "Passwords" icon, then delete everything in there, if that's what you want to do. That should keep Safari from accessing your keychain, but it also means you've lost all your stored passwords.

I thought this was strange because the username "Mike Eng" from the earlier prompts is an administrator username. Not sure if that issue is related.

This sounds like a keychain issue. Did you recently changed your user password?

If you know your old password, use that password to update your existing login keychain:

1. Open the Keychain Access app, which is in the the Utilities folder of your Applications folder.
2. From the list of keychains on the left side of the window, select "login."
3. From the Edit menu in the menu bar, choose “Change Password for Keychain 'login.'”
4. Enter the old password of your user account in the Current Password field. This is the password you were using before the password was reset.
5. Enter the new password of your user account in the New Password field. This is the password you're now using to log in to your Mac. Enter the same password in the Verify field.

6. Click OK when done, then quit Keychain Access.

Take a look at Apple's Support Document: If your Mac keeps asking for the login keychain password

This happened to me as well. Check in developer mode if you have extensions disabled, if so enable them enter your password and you should be good to go.