I got the following from Cisco Error Message Decoder.
Question: Does this mean "all" traffic will stop flowing, or just Multicast traffic? Or, just the module of concern?
. %MLSM-6-MMLS_MODE_CHANGE: MMLS: Replication Mode Change Detected
This message indicates that, when automatic detection of the replication mode is enabled, the system will transition to ingress mode when an egress-incapable module is inserted. The system will transition back to egress mode when the last egress-incapable module is removed.
Recommended Action: Transitioning between ingress and egress mode causes a temporary loss of traffic. To prevent this temporary loss of traffic, enter the mls ip replication-mode ingress command.