Original pictures from wodan:
Spoiler:
(The cases are swapped in the shots)
First solution, glueing every cracked barrel (good solution, I done it on booth keyboards).
I use epoxy with micro granulated sand (idk how to call it)
So... replacing a broken barrel (you need a spare barrelplate):
On the first keyboard I glued the barrel right on the plate, it works after all, but the switch is scratchy (but works) and it was not a good solution.
Second keyboard, now I replaced also a part of the plate and it works like a charm.
Finished: