Ubuntu 18.04 LTS LIVECD - kernel version Ubuntu 4.15.0-20.21-generic 4.15.17 - boots fine, without current issue errors
Ubuntu 18.04 LTS NetInstall - kernel version Ubuntu 4.15.0-22.24-generic 4.15.17 - has errors in console log like metioned above in this issue ("Bad kernel stack pointer", stack_trace with fast_exception_return, etc.).
Short comparison -
Ubuntu 18.04 LTS LIVECD - kernel version Ubuntu 4.15.0- 20.21-generic 4.15.17 - boots fine, without current issue errors
Ubuntu 18.04 LTS NetInstall - kernel version Ubuntu 4.15.0- 22.24-generic 4.15.17 - has errors in console log like metioned above in this issue ("Bad kernel stack pointer", stack_trace with fast_exception_ return, etc.).