The files in the folder SOI\SamUI\solr\data\index are the cause of this and this files are only of interest when you use the USM WebView from the SOI Web Interface. In order to resolve this situation please stop the CA SAM Store Indexer service on the SOI UI Server and delete \solr\data\index files. Then, if you use the USM WebView start the CA SAM Store Indexer Service. Otherwise you may leave the service stopped so it won´t recreate any new index files.
It is actually the folder SOI\SamUI\solr\data\index that must be deleted, instead of only the files in that folder. The "index" folder will be recreated after starting the Indexer service again.