For the last 5-6 weeks, I haven't uploaded anything to SS. About 2 weeks so ago, sales started to decline rapidly, and any sales I was getting were mainly 10 / 12 cent DL's.  Late last week I uploaded some new content and within a couple of days, sales rapidly improved, with far less 10 cent DL's.

This is not the first time this has happened. It's happened on a few occasions. Do SS algorithms favour contributors who regularly upload content, or is it just a coincidence?

I regularly upload content and I still get mainly 10 / 12 cent DL's, so I doubt that's a factor. Might be different if you haven't uploaded in a while. Maybe SS wants to "reward" you for coming back and motivate you to keep uploading? Who knows. Could all just be coincidence as well.

Coincidence