Lightroom Classic: Sync not working properly after Auto settings

Do you have Auto Sync turned on when you do this?

Thanks for reply! I don't ever use Auto Sync. This is strange problem, some of photos do get synced values, some don't. And after applying Sync several times it seems that all get synced atributes. Can you try? I'm CC subscriber and use latest Lightroom classic version.

I was not able to reproduce the behavior you described. My steps were:

1. Go to Develop module
2. Select 5 images
3. Make sure Auto Sync is on
4. Click Auto Tone in the Basic Panel
5. All images are adjusted
6. Click on first image
7. Adjust Contrast and Shadows
8. All images are adjusted.

Maybe you could tell me what specific steps you did?

Usually problems with Auto Sync are caused by the following. When you use the normal Sync button, you will get a dialog where you can check off which settings you want to sync. When you switch to Auto Sync you don't get that dialog; the last settings are used. And that's what people forget. Maybe the last settings were White Balance only, for example.

My steps:
1. select 1200 photos
2. Ctrl U - Auto Settings
3. select only first photo
4. change contrast and shadows
5. select all (viewing first photo with changed contrast and shadows)
6. Sync - checked only contrast and shadows

This long-standing bug has existed since at least LR 4.  I'll merge your post into the appropriate topic, which contains a couple of workarounds.