"New wget html change"

Previous RISC OS versions of wget would not let the —output-document option work when also requiring —convert-links due to a ‘file already open error’ The filestream was only being closed when wget finished, but —convert-links needs to reopen the download. The new version closes the stream and the single file will reopen for link conversion. This will allow a frontend to run a downloaded named html and have the true internet links available rather than relative links.
You probably should name the file in unix/network form like

/RAM::RamDisc0/$/latest.html