Let me try shift-selecting all images in this folder. Here goes, shift-select the range.. wait, I already see a problem! Note the circled area in the screenshot:
Now let me try again shift+clicking each one.. wow nope! No change! Windows apparently really wants those files sent in that weird order, maybe it’s a “human sort” issue? Let me try renaming them.. wow! Nope!
Note the filename area again ↑ ↑
here’s what works. Click the files you want to upload in reverse order of number. Therefore I am shift-clicking 8, 7, 6, 5, 4 and I get…
Which looks good, and when uploaded..
Upload also looks good. So this is definitely an operating system / browser issue, nothing to do with Discourse.