iCloud Photos: There was a problem uploading x files

Nearly every time I try uploading photos from a SD card to iCloud I get an error saying There was a problem uploading a number of files. Unfortunately it does not tell me which files and what the problem was. Actually, if I reupload the problem does not always show, and not with the same amount of files. All files are JPG from my camera, and the only thing I could think was that size was a problem but this does not seem to be an issue either as I have manually uploaded the largest file successfully.

The problem in all of this is that even if I try uploading again, I need to do all photos as I don't know which ones have failed to upload. This is extremely frustrating and I am now considering going back to Google photos, as I can't continuously reupload all photos when a small number has failed and I can't identify whcih ones have failed.

NOTE: I am using Google Chrome on Windows.