Spotlight search always quits itself when typing.
So on my 2015 MacBook Pro running Sierra, whenever I try to search something using Spotlight search(by the hot keys that summons up Spotlight anywhere), when I was typing in letters, after 3 or 4 letters it always suddenly quits itself , and the top right magnifying glass also disappears for a very short time(like .3 sec) and shows up again. I can summon up Spotlight again and type in and the same happens.
I tried force quit it via Activity Monitor, reset NVRAM, reset SMC, reindexing Spotlight, none of these worked.
This only happens after I successfully upgrade to Safari 12.
And looks like there are many complaints about couldn't upgrade to Safari 12 due to Spotlight app. I'd suppose there's something to do with the Safari upgrade, too.
MacBook Pro (Retina, 15-inch, Mid 2015), macOS Sierra (10.12.6)