@DaveSch Yes, I had been using 5.2.2 for several weeks before I needed to install 5.1.6. Steps should be reproducible according to the original post in this thread.
Based on what @Nick-Hall said in his reply, the change can be tracked to implementation of bug 8025, Support XDG base directory specification. I believe the flow I proposed in my reply to Nick should work, will need to try it out.