VEP unknown contigs

There are variants, eg:

https://variantgrid.com/snpdb/view_vcf/410

That are dumped with contig - vcf is good:

##contig=

HSCHRUN_RANDOM_CTG9

But VEP complains that:

Chromosome HSCHRUN_RANDOM_CTG13 not found in annotation sources or synonyms

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There is the option of ```--synonyms``` and apparently you also need to enable ```--offline``` to deal with the liftover etc