Hey, @moonunit36. Welcome to the Lightroom Community. I'll help you figure this out.
For the specific collections that don't complete syncing, try adding flags/ratings or minor edits to images not in All Photos and wait for sync to finish.
If nothing changes after some time, log in to Lightroom Web (https://adobe.ly/3uv2zCA) on a desktop with your Lightroom Account and check the Sync Issues category near the Deleted section. If there are Sync issues, check the file name, apply minor edits or tags, and wait to see if the edits sync to the cloud.
If this doesn't help, ensure you back up these images. Stop syncing these collections and create duplicate collections with different file names.
After this change, let Lightroom sync and check if it returns to normal.
Thanks!
Sameer K
(Type '@' and type my name to mention me when you reply)