meiklmue your 'fresh' install is not completing the element flashed under fastbootd.
Likely your cable doesn't meet the USB standard. What is your flashing setup?
Laptop/Desktop to Phone?
Phone to Phone?
Stock C-C Cable?
Third Party C-C or A-C cable?
Do you meet the stated requirements for OS/Browser as outlined in the installer instructions? Which combination are you using?
Also the forum is not the most responsive source for install support, our Matrix support channel is here:
However if you respond here I will try to help.