Before you do anything, boot-repair or manual changes, I highly would recommend having a backup of your EFI partition, which I believe in your case is sda2 (but you must verify this yourself before moving on). Then, you can do the following (replace the xy with the corresponding letter and the digit)
Next you can try boot-repair, and if something goes wrong, you can extract and replace the files from the .tgz you recently created.
sudo mkdir /mnt/efi_partition
sudo mount -t vfat /dev/sdXY /mnt/efi_partition
sudo tar -cvzf efi_partition.tgz efi_partition
sudo mv efi_partition.tgz /path/to/desktop/or/whatever/you/like