#9 corks come in two sizes. Some are 24mm across, others are 23mm
across. The 24mm ones are a problem for any corker that uses a sleeve
to compress the cork (hand tyle or the compressed air driven one in my
store). You may have received 24mm corks.

Some people who use hand corkers always buy #8 corks, I believe that
#8s are always 22mm across.

Despite what it says in some books & learned places. DO NOT BOIL or
even soak in hot water if the corks are pieces of chips. The hot
water/boil is OK for corks that are one piece.

Steve