"The FileSwitch module contains a special table which associates bug fixes that are needed for certain file systems. The table is associated by the file system number, and mostly covers RISC OS 2 file systems which have bugs that the later version of FileSwitch has to work around. Unfortunately, this causes problems for other file systems which reuse the numbers.

The case we found which was a problem was for IDEFS."

Noooooo....

https://gerph.org/riscos/ramble/filesystems.html#FileSwitch_FSspecialtable
#Riscos