When does the following message happen after the Find Index job runs?
An exception occured while indexing (Content): ArrayIndexOutOfBoundsException[null].
Do you have a large file somewhere like 50MB+?
or maybe there are some unusual characters in the data to index.
There is a similar error message reported this thread http://world.episerver.com/forum/developer-forum/EPiServer-Search/Thread-Container/2017/4/indexing-content-with-unusual-characters/