Okay, this happened to me on Ubuntu 20.04.1 LTS. Then it happened to me on 20.04 LTS. This happened several times. What worked for me is unplugging my Ethernet cable and disconnecting my WiFi, and unchecking the "update the OS while installing" something option. Making sure that my computer was not on the internet before starting the installation process did the trick. Hope this helps someone.
Okay, this happened to me on Ubuntu 20.04.1 LTS. Then it happened to me on 20.04 LTS. This happened several times. What worked for me is unplugging my Ethernet cable and disconnecting my WiFi, and unchecking the "update the OS while installing" something option. Making sure that my computer was not on the internet before starting the installation process did the trick. Hope this helps someone.