VEP annotation tool: "." isn't numeric in addition (+)

Question

[emma.a]

I was running VEP on a WGS VCF and in the logs files I had some warnings. In most of the cases warnings are not fatal but I would like to understand where to look in my VCF (it has ~5M variants)

WARNING: 538401 : Argument "." isn't numeric in addition (+) at .../ensembl-vep-111.0-0/Bio/EnsEMBL/Variation/Utils/Sequence.pm line 970.
Argument "." isn't numeric in addition (+) at .../ensembl-vep-111.0-0/Bio/EnsEMBL/Variation/Utils/Sequence.pm line 970.
Argument "." isn't numeric in addition (+) at .../ensembl-vep-111.0-0/Bio/EnsEMBL/Variation/Utils/Sequence.pm line 970.

How can I find which variants gives the above warning? Thanks!