I don't deal with the vendors, but every time I have to deal with one it never seems to go well.
A few weeks ago a wasp got into the dock/backroom area. It flew near me, and my phobia to the little shits kicked in and so I fled. Pepsi guy starts mocking me, loudly, in front of the TMs working in the back. "It won't sting you!" he said it like he was talking to a baby. I told him I didn't feel like rolling the dice on a $300 Epi-pen. The look on his face made it worth the lie. Then I told him I prefer Coke. That one's true.
One day I was covering a fifteen minute break for Electronics. Bose vendor walks up and starts screaming at me that the headphones display wasn't illuminated. The headphones worked, just the backdrop on the display wasn't working. I called the PMT, who came over, saw the vendor, and said "Oh, you again," and walked away. She demanded I fix it for her. I said I didn't have the tools. I had to call the LOD to calm the vendor down.