The freixenet you mention is generally fairly reliable and i've never had a
bad bottle personally although we sell quite a bit, you need to contact your
supplier as it sounds like a problem batch to me, try checking that bottles
have been stored on their sides to keep the cork moist and out of the light eg
a fridge light, i'm pretty sure its non vintage aswell so it could be getting
old, Did the wine smell musty like old cork?- could be corked although very
unlikely in a sparkler,
Six bottles though! i can just imagine the customers face I think i would have
given up after number four ;)