This is my process under Windows 10, Acrobat acrobat DC 2015.00630527
Open any file (a bit silly, but you need that to access the Search Text command dialogue box - without a document the 'Find text' from the Redact toolbar is not greyed out, but nothing happens when you select it. Which in itself is a kind of bug).
Tools > Redact > From Redact toolbar select 'Find text'. A dialogue box opens. Select the folder with 200+ files. Enter the search string, make sure it is a search string that will find a hit in +200 files. Or maybe the number of hits is the issue? In that case I think make sure you have +6000 instances found. Select them all. March checked results for redaction. Target folder: Same folder. Keep original file names. Overwrite existing files. Apply redaction marks. OK.
You will find the Acrobat halts at some point: giving strange messages. Like: ""This document was successfully saved, but an error occurred after saving the document. Please close and open again." (independent if the open document - seebeginning of my explanation- is included for redaction or some random document) " and memory errors.
This error even comes up when you keep redacting small amounts of documents but keep Acrobat open for the next batch. I guess bad memory management on the part of Acrobat. So you have to close Acrobat and reopen Acrobat even when you are working with small batches of documents.