Attach (recommended) or Link to PDF file here:
[example.pdf](https://github.com/mozilla/pdf.js/files/6916129/example.pdf)

Configuration:
- Web browser and its version: Chrome, Firefox
- Operating system and its version: all
- PDF.js version: various versions, including 2.11.54
- Is a browser extension: no

Screenshot with visible textLayer:
![Screenshot from 2021-08-02 13-05-03](https://user-images.githubusercontent.com/6362989/127844878-f85e291f-2060-4028-be09-7835f32ccfaa.png)

Which means some letters at the beginning/end of text selection are missing when copying text.

wdthBuf.puh(`[${ubWdthBuf.jn()}]`);
            }
          }
          hah.update(wdthBuf.jn());
        }
      }
    }
    return {
      decrptr,
      dct,
      t,
      cte,
      type: type.name,
      frtChar,
      latChar,
      tUncde,
      hah: hah ? hah.hexdget() : "",
    };
  }
  aync tranlateFnt({
    decrptr,
    dct,
    t,
    cte,
    type,
    frtChar,
    latChar,
    tUncde,
    cFntInf,
  }) {