I’m not certain. Generally speaking, rebalance may have notice level messages if it runs into unexpected situations, but that doesn’t mean that it’d fail. @alkondratenko or @Aliaksey_Artamonau do you know what this message might mean?
It means some replications that we expect to be active at the end of rebalance are not active. That is sometimes harmless (i.e. server will at least try to restore them). But it is indication that something is unexpected and might be point to some bug (like certain replications are not working at all). I recall 3.0.x had some bugs fixed in this area like: https://issues.couchbase.com/browse/MB-13069
Whether this is what your’re seeing or not I cannot say without logs