Safari v. 11.1.2 on a 2013 iMac… (it’s been doing this for a couple of months… don’t know when the last update was, or if it started then…)
About 20 percent of the time, when I open a new tab (or open a tab and then put the cursor in the URL field), the entire window closes. I’ve tried ALL the following, but it persists:
Safari/Preferences/Advanced - enable the Develop menu, then go there and Empty Caches. Quit/reopen Safari and test.
Safari/History/Show History and delete all history items. Quit/reopen Safari and test.
Select Library/Caches/com.apple.Safari/Cache.db and move it to the trash.
Go to Safari Preferences/Extensions and turn all extensions off. Test. If okay, turn the extensions on one by one until you figure out what extension is causing the problem.
I’m at a loss… Is there anything else I can try?