Why does Photoshop CC 2019 Build Histograms every time I switch between document tabs?

[MatthewHales]

Setup

I have two documents open. The primary doc is sort of big - 1.3GB - and the secondary doc isn't exactly small - 895MB - but I routinely work on much bigger files and have never had the issue until the 2019 update.

Issue

When I use the tabs at the top of the work area to switch from the smaller doc to the larger main doc it slowly rebuilds histograms every time. Even when nothing has been done since the last switch - just the act of switching triggers the wait bar. It's a huge momentum killer since I pop back and forth between multiple documents constantly. One note: The main doc that triggers the rebuilding was created in CC 2019, while the other doc was created in CC 2018. Switching from the 2018 doc to the 2019 doc triggers the rebuild, while switching from the 2019 doc to the 2018 doc does not.

Tech

No 3rd party plugins are installed.

My System:

Model Name: MacBook Pro

Model Identifier: MacBookPro13,3

Processor Name: Intel Core i7

Processor Speed: 2.7 GHz

Number of Processors: 1

Total Number of Cores: 4

L2 Cache (per Core): 256 KB

L3 Cache: 8 MB

Memory: 16 GB

Boot ROM Version: MBP133.0247.B00

SMC Version (system): 2.38f7

Demonstration

[gener7]

There was such a problem with CS5: Photoshop CS5 building Histograms with every file change

Chris Cox suggested:

The issue has been resolved as far as we know -- it is caused by third party plugins requesting the histogram far too often.

Gridiron and some font management plugins were triggering it.

If you don't know which plugin is causing it, disable all third party plugins and then re-enable them one at a time until you find the culprit.

[MatthewHales]

Right. I'd seen those issues, but I'm not using any 3rd party plugins.

[gener7]

I see. This is a very unusual problem, and I really don't want to say anything until I have better information.

If I find out anything, I'll get back here.

In the meantime, you may want to find out if it's a bug, so can you bring this up in Photoshop Family Customer Community

and contact Adobe Support (we are user to user forum support) to see if you can make progress.

Contact Customer Care

[dongdt]

I faced the same issue and in my case the problem caused by a very complex vector mask. Disabling it fixes the problem.