Has anyone run into odd things like those? I've encountered a few:

In Beast's Castle, I was played the "Eliminate The Deserters" Mission, using a Keyblade whose aerial combo finish involved a series of somersaults. During one of said finishers, I happened to be heading straight at the stairs. Instead of landing on them, I went straight through and landed on the ground beneath. I was just thinking "well, it's gonna be hard to finish the mission from down here," when I took a step and went through the freaking floor, into a black abyss. I was all "OH SHI-" but caught myself and remembered to Glide. Which was kinda interesting. Then I decided to let myself fall and see what happened. I eventually hit "ground" that instantly killed, going straight through my Auto-Life (also counted as my one use of that ability for that mission).

Another time, on the "Eliminate Fire Plants" mission in Agrabah, I knocked the Barrier Master's book away from him and it went right through the city wall. He couldn't get it back.

Last one isn't so much of a glitch as it is a minor programming oversight - I got 50 Mission Crowns while still at Novice rank, and was able to redeem for the items at that amount, despite not being able to see what they were on the list due to the locks from earlier freebies still being in place. There's a line of grayed-out question marks, with the check by where the number of Crowns would be, showing that I got the items, but not what the items were (10 Panacea, IIRC).

Thats strange, on the same mission in agrabah, I was attacking the barrier master in the corner wer ther is a pile of sand and i fell right through and i was in an area that was completly black, i could see my character but not his keyblade and it wouldnt let me press start so I had to reset the DS

I dodged rolled into a wall in Best's Castle and fell into the digital abyss. o_e

Supposedly in the fight with the Dustflier there's a part in the ground that makes it fall through to the bottom. It doesn't kill it, though.