Usses, my player found a wat to back at death position, how to solve?

In my server i have disabled back command, i want that players that died lose their items, so gameplay should be longer.

But, my players found a way to bypass this:

1 when they died, in menu section, select quit
2 after rejoin, thay spawn at spawn point, they open menu selection, and click respawn
3 they come back at death position

who conserv death position? i havent found any of my plugins do it, i think this is craftbukkit little bug, that at quit, put in memory death position and not respawn position after death!

Someone has advice to fix this? or some plugin?