FWIW I had several other articles to move and the results more or less bear out my suspicion that the presence of an sid seems to cause the error. The behavior was not entirely consistent though.
I got an error on
FleetTalk (Midwest), but this time I only removed the sid line from the Infobox. I was then able to move it, and had the same result moving it a second time. Note that this was before I added the "Return to DB page" link. I also got the error moving
FleetTalk Midwest Trunking Information but succeeded after removing the "Return to DB page" link (which contains an sid).
The only outlier was
Georgia FleetTalk (NXDN), which I moved without error on the first try. The only difference that stands out to me as potentially notable is that this was the only article that contained
both the Infobox and "Return to DB page" link at the time of the move.
It's far from conclusive but it may be something to pay attention to or investigate further.