When working with smart preview catalogs, the spot removal tool displays black or green squares at the site of use after a while. Not in every case, but randomly. Most often, I work with smart preview catalogs, but perhaps this does not affect in any way. These artifacts remain after export. I work on an old macbook pro with core i7 and Intel Iris Pro.
Initial troubleshooting steps:
1. Try setting Preferences > Performance > Use Graphics Processor to Off. Does that fix the problem?
2. Copy and paste here the first ten lines from the menu command Help > System Info. That will tell us the exact version of LR and Mac OS.
This morning I returned to work on the catalog and noticed that the artifacts were gone. I disabled the GPU in the Lightroom settings before I came here for advice and it did not help. It seems to me that the macbook overheated due to long work yesterday, since the coolers were noisy enough.
As for information about the system, here it is:
Lightroom Classic version: 11.0.1 [ 202111111509-eae8952e ]
License: Creative Cloud
Language setting: en
Operating system: Mac OS 11
Version: 11.1.0 [20C69]
Application architecture: x64
Logical processor count: 8
Processor speed: 2,0GHz
SqLite Version: 3.36.0
Built-in memory: 16 384,0 MB
I suggest you update to the latest LR (from 11.0.1 to 11.1) and the latest version of Mac OS 11 (from 11.1 to 11.6.3) or better, to Mac OS 12.2. The only way to get updated Mac graphics drivers is by updating to the latest version of Mac OS, and Adobe is constantly fixing bugs in LR's graphics.
I have updated Lightroom to the latest version. As for Mac OS, only version 11.16.3 is available for my laptop because the laptop is too old and does not support the latest version. However, the problem has not gone away. Moreover, when I open the catalog, I may notice how some photos with the spot removal tool used become dark. It's better to watch the video.
Sorry, Mac OS was updated to 11.6.3.