There are a few different things that could be going on, but this move might be causing some issues:
Grub stores its stuff on the EFI partition, but the kernel is stored in /boot
which is on the other partition. I don’t know if that is causing your problem or not but it seems like there is space for something to go wrong here.
Try something like this:
- Delete EFI boot entries and re-install (not update) grub, as is described in this post:
- Reinstall all kernels you would like to keep using (don’t forget to reinstall the headers too)
- Then update Grub, reboot and check again.