After wiping all cores and reindexing some 3.3 million docs from Nutch using CloudSolrServer we see inconsistencies between the leader and replica for some shards.
Each core hold about 3.3k documents. For some reason 5 out of 10 shards have a small deviation in then number of documents. The leader and slave deviate for roughly 10-20 documents, not more.
Results hopping ranks in the result set for identical queries got my attention, there were small IDF differences for exactly the same record causing a record to shift positions in the result set. During those tests no records were indexed. Consecutive catch all queries also return different number of numDocs.
We're running a 10 node test cluster with 10 shards and a replication factor of two and frequently reindex using a fresh build from trunk. I've not seen this issue for quite some time until a few days ago.