Unable to update Linux Mint due to being unable to locate repos.

I recently had the issue where I was unable to Linux Mint.
There were errors about not being able resolve various repos.
I tried updating the nameserver for the DNS and setting repos back to default an also to using local repos. Nothing worked.
I then tried clearing the APT cache and this worked. The cache was corrupted.
sudo rm -r /var/lib/apt/lists/*
sudo apt update