I haven't yet found anyone with my exact problem so I hope this isn't a duplicate post but here goes:
The short version is I get the spinning beach ball when I attempt to upload a photo using Chrome or Safari. I sell on ebay, so I do this a lot, but it also happens when uploading a profile picture or pretty much any time I have to access Photos by default.
After a forced shut down and reboot (because Quits and Force Quits don't work), all is well for a bit, but the cute little beach ball eventually returns.
This started after my official Sierra upgrade on 9/26 or so. I didn't use the Beta version. Seems to be a problem with accessing Photos specifically rather than files in general. Had no issue uploading a screenshot (below) but Chrome is currently spinning and inconsolable after attempting to add a photo to an auction.
So far, the only "fix" I've tried is resetting the PRAM and SCM. Again, it worked for several hours with no issues, but last night and again this morning, I'm stuck.
As an Apple noob, I have no idea what else to try.
Any ideas?
UPDATE: I've installed Canary and am trying that now.