@davemu,
Thanks for reaching out with this. I’ve seen similar reports before and as unsatisfying as it is, many users claim that the issue seems to just “work itself out”.
I believe this is actually an issue in Chrome/Chromium that we’ve unfortunately inherited. Can you run a test for me, and try going to Menu --> Settings --> Additional Settings --> Downloads and toggle the Ask where to save each file when downloading option “on” and see if you get the same results?
