Setup:

ACS + ASS / Insight Engine (tested with ACS 6.2.0-snapshot - latest and IE 1.4.snapshot)

Steps:

Configure IE to run with ACS in a sharded mode.
Setup a shard using say EXPLICIT_ID shading method, by specifying the following settings in the solrcore.properties.

#Shard setup
shard.method=EXPLICIT_ID
shard.instance=0
shard.key=expl:shardID

Where, expl is the custom model I added, that includes a ShardInfo aspect and has a text property <shardID>. Model is Active.

Check the sharding method is recognised as EXPLICIT_ID using Admin console > Search Service Sharding screen.
Select Dynamic Sharding to be <enabled> (or disabled)
Wait for the content to be indexed

Add some content. I added a folder, added a rule to set the ShardInfo aspect and property: shardID to 0. Then added some content to the folder.

Check that the property is correctly set and the added content is indexed on the appropriate shard (shard 0).
Using the solr admin console, check the no of docs for alfresco and archive cores (overview)
Also check the no of content returned by running a query cm:name:*.

Now, start a replica of shard 0, by using the same properties as above.

#Shard setup
shard.method=EXPLICIT_ID
shard.instance=0
shard.key=expl:shardID

Check the no of docs (overview) and no of content returned by the query using Slr admin screen.

Expected Result:
Count should match on replica.

Error:
Count does not match, as seen in the screen attached.

Also, checked adding <shard.count> property to all the shard nodes. Index for Alfresco core matches but it still differs for archive core.