@paranoid64 Technically the menu is just ipxe, but when capturing or deploying images, getting hardware inventory, stuff like that you’re booting into fos which is in the kernel and init.
You can manually make a backup of the old kernel and init that can be just as easily restored. I believe in working-1.6 this happens automatically but to be safe you can just run this on your fog server linux terminal
sudo mv /var/www/html/fog/service/ipxe/bzImage /var/www/html/fog/service/ipxe/bzImage.old
sudo mv /var/www/html/fog/service/ipxe/init.xz /var/www/html/fog/service/ipxe/init.xz.old
To revert you can simply reverse those like this
sudo mv -f /var/www/html/fog/service/ipxe/bzImage.old /var/www/html/fog/service/ipxe/bzImage
sudo mv -f /var/www/html/fog/service/ipxe/init.xz.old /var/www/html/fog/service/ipxe/init.xz
You can also name the new kernels different and specify a different kernel per host, but since this is happening before registration is recognized, it’ll be better to update globally to test it out. I am currently using the ‘experimental’ kernels in production with 0 issues.
Another thing to look at is some log files.
See if you have anything helpful in /var/log/php-fpm/www-error.log
and post it here