I don’t encounter a ORA-600 so often in an ASM instance and even more rarely on an engineered system..
I tried to add a failed disk back to the diskgroup after the replacement and ended up with an ORA-600:
ORA-00600: internal error code, arguments: [kfgpCreate_60], , , , , , , , , , , 
and as expected the feedback of the Error Look-up Tool (Doc ID 153788.1) was not satisfying.
In MOS is a note Drop ASM disk reported ORA-00600: internal error code, arguments: [kfgpCreate_60] (Doc ID 2031394.1) which don’t exactly fit because the error encountered during the rebalance, but good enough to try the solution. after setting the attribute appliance.mode to false, it worked and after the rebalance was finished i could change the attribute back to true. This attribute have no impact on smart scans or HCC, so it is transparent for the Customer/Databases.