Lightroom Classic 12.2.1
I use my keyboard arrows for navigation while moving between photos in the Develop and Library Modules. Since at least the release of version 11, maybe longer, I have noticed that after using the Sync button to syncronize photo settings most of the time the arrows will no longer work to navigate between photos. Instead I must manually move the mouse to the photo pane at the bottom and click on a photo, after this click the arrows work to navigate left and right as they always should.
Highlight 5 or more photos in the photo pane at the bottom of the Develop Module.
Make an adjustment to Color Sliders (I adjusted the hue and luminance sliders for Red, Orange, Yellow, etc).
Click the Sync botton.
Below are the Syncronize options selected
After performing these steps I was able to recreate the issue as I was making this post. The issue seems to occur about half of the time Sync is used.