So, you can recruit a number of expert traders. Among them Vault Tec Rep. So far, he's the only only one I recruited, so I'm confining this to him and to another character, who isn't a trader - Sheffield, from DD.

Everytime, you initiate a dilalogue with them, you have to go through the whole recruitment lines again, before you can barter or trade with them. This is especially tiresome with Vault Tec, since, assigning him to a level 3 trading emporium, which he hopefully carries to level 4, you want to barter with him off and on. So, I tend to avoid his shop, but that's not how it should be, does it?

Basically all of the recruitable settlers and level 4 vendors are buggy. Everyone has to go through this same dialog chain with the Vault-Tec Rep to barter with him. He goes through the "Look at us, here in Sanctuary, prepared for the future" line, then I say "Hey now that you're back here in Sanctuary, how would you like to work for me?" Then he does the "They didn't tell me much...supposed to win a pack of steak knives" line, and then finally you can talk to him again and trade with him.

I have him at the castle and he tend to hang up in, "you come visiting right" assigning him as farmer or guard then back as trader solves this for some time.

Who are the expert traders? I only know him and the bugged lady in the vault?

Personally I hate all traders in the game. I just want to buy or trade, but heck, talking to ANY of them gets you bogged down in a repetitive set of lines before you can even trade with them, Still looking for a mod that cuts out their dialogue completely and just cuts to them showing me what they have for sale. I mean like Daisy in Goodneighbor, especially after you do her library quest. She has to thank you every time you attempt to speak with her, over and over and over... I just want my shipment of supplies...

On Xbox you can spam the right trigger which will skip most dialogue, apart from that one time I somehow pulled out my shotgun and blew poor trashcan Carla's head right the [censored] off, oops.

Yeah, you can spam right arrow on the PC. Doesn't change the nuisance and immersion breakers though.