OverseerCollectionProcessor class for collectionCmd method has thread safe issue.
The major issue is ModifiableSolrParams params instance will deliver into other thread use(HttpShardHandler.submit). Modify parameter will affect the other threads the correct parameter.
In the method collectionCmd , change the value params.set(CoreAdminParams.CORE, node.getStr(ZkStateReader.CORE_NAME_PROP)); , that occur send the http request thread will get the wrong core name. The result is that can't delete/reload the right core.
The easy fix is clone the ModifiableSolrParams for every request.