I was dealing with the same purchasing lawyer on both contracts. The process was super-standard: someone sends a first draft, the other side redlines (proposes changes and makes comments), then the first team redline, etc, at some point you all compromise a bit and someone makes a clean copy of the document containing all the agreed changes for everyone to sign. So we got to the point we had all agreed and the purchasing lawyer on the other side produced the "clean copy" but he obviously thought we were a bunch of rubes so he produced a clean copy for us to sign by backing out all of our changes and only putting in his changes. This is a ridiculously low-integrity bush-league stunt and he did it on the zero-cost POC contract while we were still negotiating the >1m big contract.
Some people just want to win so bad it doesn't even matter to them that they are being total assholes, the prize is zero and it's outright harmful to their own interests. I bet he cheats when playing his own kids at boardgames.