I had no problem getting the practice arena checklist finished, however I had a glitch happen to me once and only once so far. I was testing out the D-Throw moves for my CAW and I was getting annoyed at the camera changes throwing me off as I was trying to perfect throwing them onto the steps. I went into the options to turn the camera off, and when I went back to the training arena, most of my CAW's outfit had vanished, notably his pants and his devil wings. Luckily I refreshed it by switching the wrestlers in the ring, then put him back in it and he went back to normal.
PSN: SrmKitsuneRG Games I am waiting for: MK (2011), LBP2 "It isn't a party until you have a red plastic cup." - Cooper Tom
Maybe CAWs can't do it? Because when I first started, I had a lot done with Cena (including this one) but needed springboard moves, so I switched to my main CAW. All my practice stuff got erased, so I started over. When I couldn't get it back, I switched to Rey, and he got it back for me. Then he completed the rest for the trophy.