Peppermint10 32bit Kernel 5.4.0-67-generic; Grub error..OS upgrade error..Every boots [must manually select

System: OS: Peppermint 10 Ten i686 Kernel: 5.4.0-67-generic

Problems:

1) Boot up "computer monitor@display was powered off"..., i do not know why,...
Have to MANUALLY choose "RECOVERY MODE" (every boots) to access Peppermint to login (as usual)..
2) I just want to upgrade my Peppermint....but...errors

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eddielim78@eddielim78-ThinkCentre-A52 ~ $ LC_ALL=C sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n] y
Setting up linux-image-5.4.0-70-generic (5.4.0-70.78~18.04.1) ...
Processing triggers for linux-image-5.4.0-70-generic (5.4.0-70.78~18.04.1) ...
/etc/kernel/postinst.d/dkms:
* dkms: running auto installation service for kernel 5.4.0-70-generic
...done.
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-5.4.0-70-generic
I: The initramfs will attempt to resume from /dev/sdb2
I: (UUID=b9087aef-1d3d-4224-8370-b2b7de9cf5e6)
I: Set the RESUME variable to override this.
/etc/kernel/postinst.d/zz-update-grub:
Sourcing file `/etc/default/grub'
/usr/sbin/grub-mkconfig: 40: /etc/default/grub: Syntax error: Unterminated quoted string
run-parts: /etc/kernel/postinst.d/zz-update-grub exited with return code 2
dpkg: error processing package linux-image-5.4.0-70-generic (--configure):
installed linux-image-5.4.0-70-generic package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
linux-image-5.4.0-70-generic
E: Sub-process /usr/bin/dpkg returned an error code (1)

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My Peppermint "grub.d", appended herewith: https://drive.google.com/drive/folders/1uTcfx5wj7sWdtFFYYK6aYHg5O88KF-8p?usp=sharing for your checking, tq..

Tqs for replying (with helpful guidance)....
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