The only possible explanations I can think of are that it’s either this 
…
… or a faulty Ventoy installation. Ventoy (the installer) does get updated on a regular basis, and so it’s important that you always update the Ventoy (the boot loader) on your USB sticks as well.
It’s just a thought, but for a moment there, you moved the selection bar in the Ventoy boot screen on the desktop computer to the second item in the menu, and it is possible that this somehow triggered the second entry — I couldn’t see what it was — to get booted instead of the first.
There is also always a possibility that the flash memory on the stick itself has become corrupted in some way, and maybe the second computer responds to that differently to the first computer.
Another possibility would be a combination of having overwritten the Plasma ISO with a GNOME ISO, but in combination with there being a second Ventoy installation, on the desktop computer itself, and that the machine boots from that instead of booting off the USB stick.
I’m only guessing here. It sure is a freaky phenomenon. But I doubt whether the ISO itself would be corrupt, because in that case, it probably wouldn’t even boot.
