If you arrive early morning EZE immigration can take quite a while to clear.

I've had shorter turns/transits at EZE where I didn't clear immigration. 1 I breezed through security back airside in 5 minutes. The other I almost missed onward flight due to late arrival + more than an hour to get through transfer security. Some others on the same flights as me did miss their onward connection (it seems LAN held the flight for me but not for them).