From the bug description:
CasperMD5CheckMismatches:
./pool/restricted/n/nvidia-graphics-drivers-390/libnvidia-gl-390_390.132-0ubuntu2_amd64.deb
CasperMD5CheckResult: skip
It's possible you had a bad write to your media or for some other reason
its contents could not be read correctly. Please
Exception during installation:
Sep 30 23:05:28 ubuntu /plugininstall.py: Traceback (most recent call last):
Sep 30 23:05:28 ubuntu /plugininstall.py: File
"/usr/share/ubiquity/plugininstall.py", line 1767, in
Sep 30 23:05:28 ubuntu /plugininstall.py: install.run()
Sep 30 23:05:28 ubuntu