When I leave the on arena I sometimes fall through my island and die and lose my loot quite a bit why does this keep happening

 

Its just a glitch. It happened to me a few times and all I could do to stop it was type /home as fast as I could. I only survived because on my island I spawn in water, but if you die with your things don't worry because when you respawn you get it all back.

 

But sometimes I can type fast enough and die

 

Perhaps it's because when you do /home you land on the ground and take fall damage.

 

But I don't get my items back?

 

You should pick them back up when you respawn.

 

I can't cause they r lost when I fall

 

Place water on the bedrock at your island. It'll negate fall damage

 

I think he is trying to say he falls right through his island to the void... I would sometimes do /home and end up in the lower part of my island below my bedrock and would have fell to the void if I didn't have a lower layer.

I would say your best bet to not fall to the void would be to have platform about 5 or 6 blocks below your bedrock to work as a safety net for you to land on if you do keep falling through your island.

 

I've done a platform a bit under my island and It'll be hard to break all of it and I still fall through it sometimes