Full 512gb iPhone only uploaded 100gb of 400gb of photos to iCloud, why?

It’s been a month, my wife’s old and full 512gb iPhone still hasn’t fully uploaded all 400gb of photos to iCloud (2tb), I have symmetric 1gbps fiber and wifi6 mesh… it constantly complains it’s full and points me to the manage storage settings where iCloud says it syncing… the lack of some sort of progress is just so irritating. Her new iPhone with 1tb of storage barely has much of the photos (I’m guessing 100gb worth?) that was on her original phone… what can I do to figure out how much has been upload or the progress of upload? Does upload stop if the iPhone continues to be full? (iMessage seems to be filling up the old phone in the meantime it seems) I’m keeping the old phone powered and on Wi-Fi continuously… help