Items in inventory are not listed each time you warp to a level, activate and deactive them to see what items you have, turbo's will be lost this way. (use up/down to (de)activate and left/right to change)
Items in inventory dissapear witout using them, using the shop is suspected to be the problem of this
Purchased attributes are lost when a new character is started, a workaround is to start all characters so you have all at level 1 and none at new.