Trading glitch/bug

I was trading with a race that I was friendly with and he had asked for an unacceptable trade so I had decided to try asking for a colony in addition.  When I did this it looked like it had flipped to an unacceptable trade for him then instantly flicked back to "I'm ok with trade" so I was I tried adding another colony and it did the exact same thing, by the end of the trade I owned all of his colonies but his home world. Pretty sure that is not how the trade was intended to work. I also tried this with technologies but that trade seemed to work correctly where as son as I added a second tech it said he did not agree and it stayed that way.