WHile trying to install from he July 10 2018 iso I encountered an error

[cariboo]

I used this usb drive several times to install a new version. Today it gave me an error

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: ubiquity 18.10.5 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 4.15.0-23.25-generic 4.15.18
Uname: Linux 4.15.0-23-generic x86_64
ApportVersion: 2.20.10-0ubuntu5
Architecture: amd64
CasperVersion: 1.394
CurrentDesktop: ubuntu:GNOME
Date: Wed Jul 11 23:52:47 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper only-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 18.10 "Cosmic Cuttlefish" - Alpha amd64 (20180711)
ProcEnviron:
 LANGUAGE=en_CA.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_CA.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[Phillip Susi (psusi)]

Your installation medium is corrupt; you will need to recreate it and may want to verify it using the check disc option at the boot menu.