Something similar happened to me, with the difference that the error had the output: ERROR: Failed to mount /dev/loop3, I solved the error using the same problematic USB memory, what was the problem? force the eject of the memory after the graphic window will show that the ISO copy was made successfully (I clarify that I use Ventoy).
This is a detail (it does not deserve to call it a problem since GNOME, cinnamon and KDE handle this very well) that I have been seeing for several years, although the graphical interface shows us that the copy has finished, it is still working in the background for at least 10 minutes.
SOLUTION: recreate the bootable USB, in the case of Ventoy copy the ISO and wait at least 10 minutes after the graphical interface tells us that the job is finished.
A clear sign that this happens is that the file manager does not allow us to eject the device because it is busy in some process.
the waiting time may vary depending on the power of the computer or the type of USB memory.