I have had the benefit of listening to the original communications between the Driver and Control, which have come into the public domain and from my interpretation it appears that the Driver reported that he was "maybe running fast" and had rectified a fault (with the brake ?) at Moron station which is some 20km away from destination. He also appears to being not quite sure of his train identity phrasing his identity as "the 72?" (train 72) in a questioning manner. There appears to be some confusion with the Controller as to what he was talking about. The Driver then goes on to say that he had rectified the "grip". The problem is that South American spanish has its own variations between Countries which makes it difficult to fully translate, as even Argentinian and Venezualan spanish (in which "language" I was giving Spanish langauge training) are somewhat different in detail.
An amusing example is shirt which is "camisa" in mainland Spanish but in Argentinian Spanish if used to describe a T shirt, translates as "high class hooker" !
As regards the buffers, there are only central auto couplers fitted. The second carriage overode the first which is the normal scenario in this type of collision. Traditional buffers are not intended or designed to reduce collision but to soften traction braking shocks.
Normal coupling up is done at much less than walking pace, with the traction unit stopping short of the train it is coupling up to and then moving forward gently.
The only other recordings said to be involving the train are immediately after the collision at Once