I’m running into a similar problem, so far redoing the installation doesn’t seem to get around this:
E: Failed to fetch http://archive.lambdalabs.com/ubuntu/pool/main/n/nvidia-cudnn/libcudnn-dev_7.6.5-0lambda1_amd64.deb Hash Sum mismatch
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?`