If the BMI Server Setup feature is used to reconfigure a channel, either by you or by another user, the original files will be reinstalled and will overwrite the symlink and the linked file.
To make sure you can recover from this overwrite:
Maintain a backup of your customized files, both template and host files.
Check that the symlinks point to the correct file; fix them if necessary.
Check the /tftpboot/images/TYPE/ARCHITECTURE/DISTRIBUTION/ directories. The file that was linked will have been overwritten. Replace it with a backup version.
Check the //BMI-system/tftpboot/pxelinux.cfg/MAC-address/ directories. If your host file was overwritten, replace it with a backup version.