It seems to be a serious issue.
Now I tried to upload a very small file 358 KB.

The upload progress bar showed ...

120/359 KB and dropped to 70/359 KB
120/359 KB and dropped to 70/359 KB
120/359 KB and dropped to 70/359 KB
120/359 KB and dropped to 70/359 KB
120/359 KB and dropped to 70/359 KB
120/359 KB and dropped to 70/359 KB
120/359 KB and dropped to 70/359 KB
120/359 KB and dropped to 70/359 KB

And

140/359 KB and dropped to 80/359 KB
140/359 KB and dropped to 80/359 KB
140/359 KB and dropped to 80/359 KB
140/359 KB and dropped to 80/359 KB
140/359 KB and dropped to 80/359 KB
140/359 KB and dropped to 80/359 KB
140/359 KB and dropped to 80/359 KB

And

So on ... Increasing and decreasing continuosly.

It took 9 mins to upload 358 KB.

And Uploading a 24 MB file seems to be impossible.