Indexing errors

I notice regularly indexing errors. When I next hit the cross of the indexing, there is this error message shown:
"500 Incorrect string value: '\x93Voor ...' for column `dedecani_j4`.`j40_edocman_documents`.`indexed_content` at row 1".
This an example of more failed indexes, which I cannot correct..
In the past these pdf documents have been indexed several times bij Edocman without a problem.
Please advice.

In the meantime I decided to completely  remove Edocman from my website and from the Database.
Then I installed Edocman fresh and my problem has gone. Thank you.