The SCF repair happens every time SCF runs, not multiple times in one run. The file is [1:22{11}]"simsunb.ttf" and it does say it has copied it "from store" each time. Both this file and the bad blocks are on the System partition. Considering what "simsunb" is - and the fact that I don't read Chinese - I could very well get by without it.
My understanding was that the parameters I used for Chkdsk included /F but performed more checks as well. That is on the data partition - on the system partition it schedules a check at restart.
The partition where I had the original problem comes up clean in Chkdsk. I renamed the folder and renamed it back, and that cured the problem of Windows Explorer crashing. I don't like that sort of 'cure'...