For more info go to the Metal Gear Wiki.
Haven't seen this being noted anywhere else, so I'll add it here. While in Bolshaya Past South, near the helicopter, for some reason Snake began acting as if he was bumping on an enemy, even when no one was near him. Due to this, he could not hold enemies, but he was still able to knock them down. Dunno what caused it and I was unable to reproduce it. (PSVita version from MGS2 & 3 collection)