[c-nsp] blackholed traffic on ether-channel

[selamat pagi]

Setup:
4 port LACP channel, C6880 <->  Nexus 7k

Recently we had the issue that most (not all) traffic was black-holed on a
C6880.
No interface counters, nor the port-channel status, nor an NMS pointed to
any abnormal behavior.

Finally, the problem was resolved by shutting down a specific  interface on
C6880.
It seems that one defect port affected the function of the entire
port-channel !!

Have you ever encountered a similar issue ?

How could these be monitored ?
Would a ping across each link  be a recommended  approach (load-balance
hashing would need to be considered)?

cheers, keti