There was unexpected progress, posted at Physics Stack Exchange, on two problems that were low on my list.
First, numerology of the charge radius. See my 2017 update: I ran across a model of the nucleon in which the radius is 4 natural units, divided by the mass. That doesn't explain why the radius comes out a little different for muonic hydrogen compared to electronic hydrogen; but it can explain why dandb's ratio is approximately 4 in both cases.
Second, mystery of the Z0 decay width - that it lies on the same curve as a number of mesons. It's one of @arivero's minor observations, and not one that I spent any time on. I was just going through the motions of investigating it, when to my surprise, something turned up.