I have complained several times about getting bad 10ml flavors in my first DIY order from now-defunct CompanyX. I never mentioned that I also got shitty oxidized Nic too. I think the urge to save a few bucks going to some of the lower volume (lower cost?) Sellers is ill-advised.
Since that first order I have purchased from the top Sellers like Bull City and NicRiver and have NEVER been dissatisfied. Doubtful that bad nic or bad flavs are the cause of the sore throats, but it sure wrecks DIY enjoyment overall …and oxidized Nic sure is not helping! Point being… saving a few bucks in this arena may instead be throwing your money away.