After importing and editing images in LRC they will not sync to the cloud unless I restart LrC.

FWIW, I still see the same mainly consistent behaviour. Specifically, I take a few images with the LrM Indigo camera app, wait for them to sync across the system and down into LrC. Once in LrC I then remove them from ASP, wait for the images to disappear from the cloud, then if I immediately resync them by adding to a synced collection without making any changes to the images (e.g. no added metadata), the images sync without issues.
However, if after removing from ASP I then add some metadata (ratings, keywords etc.) before adding them to a synced collection, the sync stalls and usually requires an LrC restart to get them to sync.

I've repeated that process several times again this morning with the same results. For one test I removed 4 images from ASP, then added metadata only to two of them before adding all 4 back to a synced collection, and the resulting sync stalled. Removed all 4 again from ASP and then added only the two without the added metadata back to the synced collection and they both synced correctly. Added the other 2 with the added metadata back to a synced collection and again the sync stalled.

Quite puzzling.   On aug 15 (as I recall), I was able to replicated the problem using the steps I outlined in response at that time (why doesn’t this forum show post dates or post# in thread?).   However yesterday, running the exact same steps everything synced just fine with nothing getting stuck.  Different photo, but taken with the same Pixel7 camera (native camera app) and the same settings.    

I just tested again with a couple of photos and the problem persists. I left it for a good hour to sync this time but it was having none of it. After a quick remove from "All Synced Photos" and a LrC restart they synced to the Lr cloud in seconds.

However, yesterday I was playing around and doing some tests and initially the same problem ocurred. But after I had done the restart and synced those non syncing photos to the Lr cloud I decided to upload some more photos from my phone just as a test. To my surprise, after going through the usual steps these photos synced to the Lr cloud first time with no issues. Its as if the initial restart cleared whatever blockage was preventing sync and the blockage never came back even with further uploads. Most strange.

This issue has been replicated (in part) by LrC experts on the Lightroom Queen Forum, but could then could not replicated again.

I’ve also run a lot of tests of the “replace originals with smart previews” workflow since ​@marknicholas88 reported the issue both here and at the LightroomQueen forum. I can replicate the “stuck syncing” issue but ONLY if I add metadata or develop edits to the copy of the original image in LrC BEFORE then removing it from All Synced Photographs and re-syncing it as a smart preview. If I do the removal from ASP before doing anything to the image in LrC, adding back to the ASP syncs the image to the cloud without issue. In most of the tests it didn’t matter if I added the metadata before or after re-adding the image to the ASP collection, though with one test only it did stick syncing when I added metadata before re-syncing.

I’ve run quite a few tests and consistently got the results as described. I’m using MacOS 26.5.1, whereas ​@marknicholas88 and ​@Califdan2 are Windows users. That may or may not be a factor.

Tomorrow I’ll try the above scenario again but will substitute a develop module change in step 5 and in step 6 will drag image to “All synced Photos” special collection rather than some other synced collection.  This will determine if the hang up is related to there being a metadata change.

Try deleting the photos from the “All synced Photographs” before restarting LrC. Then resync the photos again after restarting. 

I replicated your problem - but not your solution:

1. Took photo with default camera on Android phone (jpg)
2. Imported photo in LR/Android on my phone
3. Image synced to LrC and was placed in a the designated folder and was added to the "All Synced photographs" special collection
4. Removed image from "All Synced Photographs" special colleciton (which caused it to be removed from LR/Cloud) - verified in LR/Web and LRD
5. Assigned Keywords title and caption in LrC and gave image 3 stars
6. Dragged image to an already synced collection
7. It did not sync and stayed "syncing 1 image" and stayed in the "sync activity" log in preferences with a status of "Uploading"
8. Waited 10+  minutes - no change
9. Shutdown LrC
10. Re-Launched LrC (took significantly longer to open than normal)
11. LrC still showed 1 image syncing and EVERYTHING in LrC  excruciatingly slower than before the shutdown of LrC (e.g., minutes rather than seconds to just change active photo)
12. Shutdown LrC again
13. Re-launced LrC and it came up in seconds (rather than minutes) as is normal and performance back to normal
14. Still showed 1 image syncing which will not complete
15. LR/Web does not show the image

This indeed seems to be a bug.   But, your workaround of shutting down LRC and re-launching it does not solve the problem on my machine.    I updated your bug report with the above information.