The most probable cause is either an defective ISO file - you verified the checksum - so there is the or - a defective USB.
I suggest you try using the manjaro-get-iso package and test the download directly to your mounted Ventoy partition. The script is Python, should be distro agnostic
$ get-iso -h
usage: get-iso [-h] [-f] [-o OUT_DIR] [-t TEMP_DIR] [-p | -r] {plasma,xfce,gnome,cinnamon,i3}
This tool will download the latest ISO for a named Manjaro Edition (default: minimal)
positional arguments:
{plasma,xfce,gnome,cinnamon,i3}
Edition name (only gnome, plasma, xfce is valid for (p)review)
options:
-h, --help show this help message and exit
-f, --full Download full ISO
-o, --out-dir OUT_DIR
Folder to store dowloaded ISO files (default: current directory)
-t, --temp-dir TEMP_DIR
Location to store temporary files (random tmp folder: /tmp/tmpu_z5uqyf)
(P)review:
-p, --preview [Github] Developer Preview
-r, --review [Github] Release Review ISO
get-iso v. 0.17.0 - MIT License <https://opensource.org/license/mit>
For an official release ISO, the script will
- download into a temporary folder
- verify by signature
- copy the ISO to the destination - your USB
- finally verify the by checksum
Also be sure not to remove the USB before the copy has been done.
If you have the package udev-usb-sync installed - the ISO should be complete when you hit the eject button in your file manager.
[INFO] New package - udev-usb-sync
[INFO] New package - manjaro-get-iso application