It would help us tremendously if you provided:
• Version of Acrobat
• Operating System
• Sample before and after PDF files exhibiting the problem (pointer to such files)
- Adobe Acrobat Pro DC
- Windows 7
- The examples I have are confidential documents
Unfortunately, without seeing what's gong on, it's very hard to provide any help. You say this happens on multiple computers, but does it also happen with other PDF files? I would test files from different sources to rule out problems with files created by the same system.
What software did create these files? You can find out by opening up the document property dialog (Ctrl-D). The "Description" tab has information about the "Application" used and the "PDF Producer" that actually generated the PDF file.
I've never seen any distortion or other ill effects when using the redaction feature, that's why I am pointing at the specific PDF file (or files from the same source) as the factor causing this problem.