Upload progress bar jumps a lot when starting uploads in multiple batches

[jpxd]

Description
I start an upload of 10 big files (5GB total). The progress bar shows the progress increasing slowly, so far so good.
A few minutes later (the first upload is still running) I start an upload of another 1GB file.

Expected behaviour
When starting the second upload, and the first upload is still running, the progressbar should jump back a little and continue from there, as the overall upload progress decreases when adding new files to the upload queue.

What is happening instead?
The upload progress bar jumps a lot between the progress of the two upload batches which are running.

Additional context
See this screen capture:

How to reproduce?

• Upload a few big files (so big, that it takes a few minutes, like 5GB)
• After one minute upload another big file (like 1GB)

Files
Any large files work.