I've also had this happen on my bike
, but the damage wasn't too serious
, all I had to do was replace one of the cush drives.
When you get new ones fitted, use a centre punch and peen the sprocket in about 3 or 4 places around the outside each of the drives as this will stop the drives working their way out and then protect the peen mark with a blob of paint.
If you don’t understand what I mean, get in contact (u2u) and I can send you some diagrams.
If you think that this procedure is a bit dodgy, the aerospace industry has been using it for years on bearings and we use it in all sorts of places in the F1 team that I work for
.
Regards,
Gannet