i am trying to upload my photos to onedrive via the web. I dont do it via the windows sync app as I dont want this folder synced as its too big.

I know all the fragile problems with onedrive, and can confirm that:

all my file names are < 8 chars + ".jpg"
None of the filenames nor folders have any chars other than ascii
There is only one level deapth (a directory with files in it)
I have 300GB of space left in my 1TB (so its not a space issue).
Files are all < 10MB, so its not a file size issue.
I have tried with different folders of images, always same problem.
I have 300Mb symmetrical uncontested fibre connected via 1GB Ethernet and managed switch. speed test.net shows 310Mbit up and down 100% of the time.
How to reproduce:

open onedrive.live.com in either chrome or IE (both fail)
navigate to my pictures backup dir in the web view of onedrive.
drag a folder of images (or just images, same problem)
It very quickly uploads a small number of the files (between 15 and 20)
Then it says "uploading *** items" in the top right, and when I click on it it says "Progress uploading *** items to picture_bacukups"
Then nothing happens. It makes no progress, it just hangs. I have tried leaving it for 3 hours, nothing happens.
It creates the target directory and a few initial image files (it usually manages around 15, I have tens of thousands in total to transfer (not all at once of course, it certainly cant handle that)
The browser and onedrive website are still responsive, e.g. I can open a dir (and it still says "uploading *** items" in the right corner)
This also happens if you try to copy the missing files from a directory. Drag say 500 images to the dir in the web browser, and it uplodas say 15 then simply doesnt upload any more, it gets stuck. close the browser, start again, drag the remaining 485 files, and say 17 of these get copied, then it stops again. Something is very wrong.

Several months ago this used to mostly work, but now I am stuck - there is no way to upload files. I have been trying since 2 days. after several hours of no files being uploaded, I close the browser, delete the partially uploaded directory, and start again. Always same result - it creates the dir, uploads a random number of files (between 15 and 17), then simply stops uploading for no reason.

I found this thread where people are having exactly the same problem with no solution:

https://answers.microsoft.com/en-us/onedrive/forum/odwork-odfiles-sdwin10/onedrive-upload-stalls-when-trying-to-upload-a/590140af-90f6-4ad8-aa43-ad99fb1162a4

I tried again a week later, and the problem is exactly the same, It always hangs after uploading the firs few files.