In Safari, there is a lag for the Open Location and New Tab shortcuts.
Launch &quot;Console&quot; and have it running side by side with Safari. See if entries about &quot;IMKServer&quot; appear when the delay happens: 
If you see similar entries try following below: https://gist.github.com/wkrsz/3d5ff7f908a180b87498
Steps from the article:


Reboot into system restore mode (+R immediately after boot)
Navigate to Utilities &gt; Terminal
Enter the command csrutil disable
Reboot
Open Terminal
defaults write -g ApplePressAndHoldEnabled -bool false &amp;&amp; launchctl remove $(launchctl list | grep -oE 'com.apple.PressAndHold.+$')
sudo chmod 000 /System/Library/Input\ Methods/PressAndHold.app/Contents/MacOS/PressAndHold
Reboot
You can choose reboot back into restore mode and issue crsutil enable again to re-enable rootless mode.


It's originally from Github user squeeb: https://gist.github.com/squeeb/5a9dd082cae1b2d753a0 – I just forked the article to fix a typo in one command.