It happened to me once. And worst part is that it happened to me when I was negotiating a seed round :/
So, I ended up stoping negotiations with the BAs and focusing on raising a personal loan to buy him his shares.
Finally I was able to buy him out and signed with the BAs (who were extremely supportive in the process because they saw me manage all of this professionally... and I didn't use their money for my battle).
So, if you really don't hit it off with him, my advice is only one: "the sooner the better".
So, I ended up stoping negotiations with the BAs and focusing on raising a personal loan to buy him his shares.
Finally I was able to buy him out and signed with the BAs (who were extremely supportive in the process because they saw me manage all of this professionally... and I didn't use their money for my battle).
So, if you really don't hit it off with him, my advice is only one: "the sooner the better".