MacBook Pro 2019 Touch Bar lagging when Changing Volume
I’ve had issues with my touch bar too. (See Touch Bar not turning on after waking computer from sleep.)

Here are some things that didn’t work for me, but they might work for you:


Open Activity Monitor, find and select TouchBarServer, then press the Stop button. Then select Force Quit. It should restart automatically and your touch bar should be back to normal speed and responsiveness.
If step 1 doesn’t work, try resetting your SMC:
https://support.apple.com/en-us/HT201295
If step 2 doesn’t work, try resetting your NVRAM/PRAM:
https://support.apple.com/en-us/HT204063