Trouble redacting

I have to be able to redact pdfs but am having an issue with a particular document type. It is saved as a PDF, as are most other documents which I manage to redact wthout issue. When trying to redact, it highlights either multiple long narrow columns or a really random geometric shape. I had no problem initially and my co-workers do not have this issue. All documents are saved in the same way so this is just an issue I have. I am having to use a work around but this is not ideal.