Can’t help youhere unfortunately, as I would have thought that this is the most likely cause as well.
I’m just commenting to say: Please let us know if you found a solution to the problem. I’m very interested to know what might have caused this.

I actually needed to look that up, since I didn’t know either. So, thank you, I’ve learned something new because of your question.

          d/s    The number (after merges) of discard requests
                 completed per second for the device.

          f/s    The number (after merges) of flush requests
                 completed per second for the device.  This counts
                 flush requests executed by disks. Flush requests are
                 not tracked for partitions.  Before being merged,
                 flush operations are counted as writes.

https://man7.org/linux/man-pages/man1/iostat.1.html

(Discards being TRIM operations on SSDs, I imagine.)

Yep, that was the issue.

This post reads like it’s written completely by AI, which means the software is (most likely) written completely by AI.

Edit: Also, no TLS? Are you kidding me? I’m supposed to upload my documents over an unencrypted transport?