[BUG] Syslinux-efi64 6.04 doesn't boot OVMF's machines

Hello. I’ve tried to boot a Fedora 31 UEFI x86_64 VM via Syslinux instead of Grub, using either VirtualBox or Qemu (which implement OVMF UEFI). Using the “syslinux-efi64” package, which ships v6.04, i can’t see even the menu because boot stucks. But if I download a v6.03’s syslinux copy (for instance, this:
https://openmandriva.pkgs.org/4.0/openmandriva-main-release-x86_64/syslinux-efi-6.03-4-omv4000.x86_64.rpm.html), every it’s ok. What it worst is that the “syslinux-efi” package from Ubuntu works perfectly when I want to boot an Ubuntu 19.10 UEFI x86_64 VM machine, which it’s very strange because this package ships the v6.04 too, like Fedora.
Is there someone could give me some clue about what is happening and if it’s really a version problem?
Thanks a lot!