CrossMap lift over bed but not the same vcf file

Question

[Medhat]

Trying to see what is happening from the previous post CrossMap liftover failed

I downloaded a vcf file from ftp://ftp.ensemblgenomes.org/pub/plants/release-31/vcf/zea_mays/zea_mays.vcf.gz and try to lift it over using CrossMap also it did not work
But when I convert the vcf file to bed file first using vcf2bed from bedops package and the I lift it over using CrossMap it worked !!

any suggestion here? or explanation for this behavior