FreePBX17 can't get debian to boot a different kernel by default

Distro Discussion & Help
1

I’m stuck again on something stupid.
I had to downgrade the kernel in order to in order to install with dadhi (–dahdi)
Now I can’t seem to get it to boot anything other than the original default (newest) kernel
The one I want is 1>4
run update-grub and reboot.
It is not working and just seems to be booting the original default.
I also tried the save last selection option and this does not work either.

Including trying:
Add two lines to /etc/default/grub

GRUB_SAVEDEFAULT=true
GRUB_DEFAULT=saved

I can boot the kernel manually just fine by going into advanced options and choosing it.

2

Have you tried removing the newer kernels and keeping only the DAHDI supported ones installed ?

3

No, because I’m not exactly sure how to do that at the moment..
This is an opportunity to make the system unbootable.
Which I do not have time for at the moment.

4

This is what we ended up doing today..
Frustrating that I could not get it to work the other two ways mentioned following any and all instructions I could find anywhere which claimed it would work.