I eventually found out that the problems were psychosomatic. The key observation was that when I started reading John Sarno's "The Mindbody Prescription", my symptoms suddenly started shifting from wrists to ankles. "Hey wait a minute…" was my thought — and it turned out that my mind was the cause. I don't buy all of Sarno's stuff, but even thinking about this and considering it carefully caused major effects for me.
Fast forward many years, and taking care of my mind helped my overall health tremendously. Many problems I had are simply gone. And I have a finely tuned radar now whenever something new appears — if it isn't easily diagnosable and attributable to a medical problem, it's likely psychosomatic.
For those unaware: psychosomatic issues are not "hallucinated" nor are they hypochondria. These are real issues, just caused by your mind, for example causing muscle tension or restricted blood flow.
Looking around me, I can see many people whose issues are likely psychosomatic. Unfortunately, it's very difficult to help them, because "no one can be told what the Matrix is, you have to see it for yourself" — you have to be ready to accept this explanation and deal with the mental problems.
Obviously not all RSI problems are psychosomatic, but at least some are, so it's worth looking at.