P: Hang while using Shawdows/Highlights tool with the Histogram panel showing (macOS)

That's an infuriating response. If something worked yesterday, and a software update makes it stop working today, it's a bug, period. 

After contacting support via the on-line chat the Photoshop technician clearly stated that this was "not a bug". After allowing them access to my computer it was stated that the presence of "BitDefender" anti-virus was the culprit (though why there had been no problem before Photoshop 21.1.0 isn't clear to me). Removal of BitDefender and then uninstalling/re-installing 21.1.0 by them seems to have done the trick.

I have been in touch with BitDefender and they say try re-installing the anti-virus program and if there is a problem they will troubleshoot it and resolve it without having to go back to Adobe. However, for now, I am a bit dubious about following their suggestion.

Has anyone else with problems got BitDefender installed? Does anyone have any comments about reinstalling Bit-Defender?

Having the same issue, every time I try and use the shadow and highlight tool. On a whim decided to uncheck the preview and move one of the sliders and it didn't crash/freeze. That defeats the purpose of using the tool though if you can see the adjustments as you make them.

Mac OS 10.13.6 with PS 21.1 and was using it during an NHL game tonight and shadow highlight worked fine at the first-period break. The second-period break it would lockup PS and the computer until PS was closed. No changes after a reboot. 

Hi, I noticed that on my MacMini after last MacOs update S/H adjustment Photoshop crashes, while on my MBP without last MacOs update it works, Can the two thing be related?? Can it be a problem from MacOs update and not from Photohop 21,1 update?? Don't know what to think...

It there a year bug in the scripts of updating of PS 21.1.0 if you have an ancient version on your ord. in first, to abolish this ancient version as well as all personalizations possible, reboot the computer and made a new installation of PS 21.1.0 but especially do not remind of before safeguarded shape, it is in one of saved parameter that there is a bubble!

I am getting hanging on Shadows and Highlights on an iMac running 21.1.0 under Mojave 10.14.6 OS and also on a latest version fully spec'd Mac mini al.so running 21.1.0 under Mojave10.14.6 and it happens whatever image I am attempting to edit with the jpg. images originating on Olympus, Panasonic and Sony cameras. as soon as I attempt to move a slider I get spinning beachball and end up having to force quit Photoshop via the Mac's Activity Monitor. This is a definite bug.

After further experimentation I found that the hanging only happens if you use the sliders in Shadows and Highlights. If you enter percentages in the boxes the adjustments work without causing Photoshop to hang.

So the bug relates to the sliders. It needs resolving asap.

Adobe, please look at my post hier up : https://feedback.photoshop.com/photoshop_family/topics/photoshop-21-1-0-after-latest-update-app-hangs-while-trying-to-use-the-shawdows-highlights-tool?topic-reply-list[settings][filter_by]=all&topic-reply-list[settings][reply_id]=20435402#reply_20435402

It is the same to me. Today Iv'e updated to 21.1.0 and it's been failing. Mac Catalina 10.15.3 AMD Radeon R9 M390. Hope this can be fixed soon.
UPDATE: Uninstalling and Reinstalling the Version: 21.0.3 solved the issue for now.

Exact same thing happening to me on MacPro running 10.13.6 after update to 21.1.  Shadow/Highlight tool causes freeze.  Have to force quit.  Haven't tried it yet on MacBook pro running Mojave.  
Have resorted to using Photoshop CC2019.
Please fix asap.