Names of items in inventory are not shown each time you load up the game. Activate and deactivate them in the tower to see what items you have, turbos will unfortunately be lost this way.
Items in inventory disappear without 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'.
The eleventh item you hold at any given time will go into an inventory slot that can't be accessed for that character's entire lifespan. To get around this, be sure the eleventh item is something you don't want, like a gas mask or one of several breaths/amulets. The shop's a good way to do this.
Scrolls will sometimes randomly cause the game to freeze, especially in the Ice Domain realm.