Splitting the beam on a leap results from twisted hips, if the hips are squint in splits on the floor, they will be quint in the air. This causes the body to lean to one side and therefore the gymnast splits the beam
Another common cause of this is gymnasts with inturned feet, if a gymnast lands on the beam with a turned in foot they can split the beam.
about two weeks ago I straddled the beam on a side aerial. well I guess it was more of a butt slide It was on a friday before a meet. I was like great! lol I had hit my butt, my hamstring, my shin, and hurt my thumb. lol my shin was all bruised up. Luckily my aerial is right before my dismount. so I just got back up and did my dismount. I was just laughing through it because before my fall my routine was like really good. with the fall my coach judged me at about a 9.35.
I kind of did once on a regular leap (haven't ever done it on a switch leap) but I basically caught myself. I was an optional at the time too so I have no idea what the heck I was doing. I've split the beam on other things though, flight series mainly. I had a mark on my leg that was visible for like a year after missing my hand on a BHS series.
Worst crotcher I've ever done was when I was doing a full turn with my leg at horizonatol on the high beam. It was gorgeous... except for I missed my foot! I meant to put it beide me, but missed the beam and went right down into a crotcher! Ouch!!! I had bruises on the inside of my legs right to my knees.
My DD came out of practice one day a year or so ago telling me that she had "crouched the beam." I had no idea what she was talking about, until my friend, who had been watching practice, leaned over and whispered, "She means she 'crotched' the beam." O.K. I got it then, even though I had never heard the term before.