Does Ubuntu 19.04 has an installation bug?

My Ubuntu 19.04 is a torrent download from April 18. It does not start after installation.

On my 128GB SSD I have a 60GB partition for Windows and two 30GB partitions for Ubuntu and of course another 4GB for SWAP. One Ubuntu partition holds Ubuntu 18.10. That version of Ubuntu works. Into the other Ubuntu partition I tried to install Ubuntu 19.04. I tried that three times. It came up with different problems. Once I was able to key in my password, but it stayed in a loop, asking me again and again to key in my password. In other cases the screen was scrambled. So I thought, it might be a defect of my SSD.

So instead of 19.04 I installed into that partition a second version of Ubuntu 18.10. That installed flawlessly.

I then installed Ubuntu 19.04 into the partition which was holding the original version of Ubuntu 18.10. Again Ubuntu 19.04 did not start. It kept asking me for my password in a never ending loop.

What can I do to make Ubuntu 19.04 run on my ASRock PC?