Shattered glass can come
Shattered glass can come from a number of things ranging from advancing the temperture too fast, mixing with incompatible glasses, to insufficient separators.
Glass running off the area can be from being too hot to being too thick.
Much more information is required from you to answer adequately. Give conditions when these things happened. info on schedules, and on kiln type (side/top/combination elements), etc. would be helpful.