Be sure to include the first ten lines of the menu command Help > System Info. Provide all the details, rather than linking back to this thread -- experience shows that Adobe developers tend not to follow the links.
I recommend that you include: how many photos you're syncing, the file types (raw, JPEG, DNG, etc.) and pixel sizes of those photos, the camera model, and which settings you're syncing. A screenshot of the Sync dialog would help, and a full-resolution screen recording even better. (You'll have to upload the screen recording to Youtube, Dropbox, or similar and include the sharing link.)
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