Not sure if this is also relevant but I thought I would post it here for good measure. One suggestion was to repair the filesystem using fsck command, however, sudo doesn't work within GRUB, recovery screen crashes and my only access to a terminal is through the USB stick with Boot-Repair.
Code:
mint@mint:~$ blkid
/dev/sda1: UUID="12E4-D300" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="3442d9cf-e5f1-4325-a068-240abd71713a"
/dev/sda2: UUID="01d64bdc-d66f-47f8-b164-16401ffdc95d" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="abc10a7e-b1d3-4855-b27e-5a626b78391b"
/dev/sdb1: LABEL="BOOT-REPAIR" UUID="2EF0-291B" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="0281a0c6-01"
/dev/loop0: TYPE="squashfs"
mint@mint:~$ fsck /dev/sda2
fsck from util-linux 2.37.2
e2fsck 1.46.5 (30-Dec-2021)
fsck.ext2: Permission denied while trying to open /dev/sda2
You must have r/w access to the filesystem or be root
I'm assuming you can use the Boot-Repair USB stick to repair the boot-loader on (sda2?), however, I'm uncertain on how to do this.