When using FAST search for SharePoint 2010 (F4SP) to crawl a content source that contains managed metadata in the field you might get this error
The SharePoint item being crawled returned an error when requesting data from the web service. ( Error from SharePoint site: *** Index was outside the bounds of the array. )
this is because one or more metadata field is filled with incorrect value. When you open it up it show something like this.
The red underline text means there’s no term “Knowledge” in the Knowledge Themes metadata field.
if you leave this red text save in your item properties and run a crawling. You will get this error.
To solve this error
That’s simple, correct the red underlined text in metadata field. then FAST search will crawl this item correctly.