If it works fine with 8GB USB and fail with 256GB USB.
It's very similar with the case bellows. But this is only for legacy BIOS mode.
https://www.ventoy.net/en/doc_legacy_limit.html
Please make sure that this problem occurs in UEFI mode?
In the lower left corner of ventoy's boot menu, it will show current BIOS mode.
1.0.13 BIOS www.ventoy.net ---------> Legacy BIOS mode
1.0.13 UEFI www.ventoy.net ---------> UEFI mode
It's very similar with the case bellows. But this is only for legacy BIOS mode.
https://www.ventoy.net/en/doc_legacy_limit.html
Please make sure that this problem occurs in UEFI mode?
In the lower left corner of ventoy's boot menu, it will show current BIOS mode.
1.0.13 BIOS www.ventoy.net ---------> Legacy BIOS mode
1.0.13 UEFI www.ventoy.net ---------> UEFI mode