Every hour or two, the Update Manager keeps giving me an error message saying that my APT configuration is corrupt and that I should switch to another Linux Mint mirror. It usually goes away when I do a manual refresh but it just keeps coming back. I have also tried switching to a different mirror but I get the same error. It also tells me to run apt-get update but even if I add “sudo” it just gives me an error message saying to run apt-get update.
Boot up from a USB drive that’s what I did. I was just about to add the merge list in the update manager as well. Keep me posted if it didn’t work. Best of luck.