I keep hearing about it happening, but it hasn't happened to me yet.

But...

Originally Posted by fylimar
It happens all the time to me. It seems to be triggered, when you switch between characters to sell stuff.
So now, I give all items, I want to sell to one character and only interact with that character - that works better.

...this is how I do all my interactions, so maybe that's why I'm not experiencing the bug.

I also do all my trading via barter. (I can't imagine why anyone would want to use the other option.)