|@Phil, LOL nah, man, it's very simple.|
Those files in my urls directory were inaccessible to EDIT and FINDSTR, but accesible to FIND, COPY etc. I think I figured out why: a leading "?" in the filename. Best bet is to copy the file to another name before trying any other operations:
for /f "tokens=*" %%a in ('dir /b^|findstr /r "^?"') do copy %%~sa %%~saz
makes a new short-name file with "z" added to the extension. Not elegant, but at least the file is accessible for other operations. I avoided moving or renaming for logistic/security reasons.