Awesome! This question has already 2 answers..
this may be caused also by anonymization type (currently unavailable to change for vultr), but this feature has already been added for Amazon and Google - so you may select if you want send header to target site or random header or no header. Somehow for VULTR is set default no header option, so this may be reason & soluction in once.
As I said already, VULTR will be updated, maybe even today, so this option will be added.