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.

nf("graphc tate peratr "  key);
          break;
        default:
          nf("Unknwn graphc tate peratr "  key);
          break;
      }
    }
    return prme.then(functn () {
      f (gStateObj.length > 0) {
        peratrLt.addOp(OPS.etGState, [gStateObj]);
      }
      f (SleGState) {
        lcalGStateCache.et(cacheKey, gStateRef, gStateObj);
      }
    });
  }
  ladFnt(
    fntName,
    fnt,
    reurce,
    fallbackFntDct = null,
    cFntInf = null
  ) {
    cnt errrFnt = aync () => {
      return new TranlatedFnt({
        ladedName: "g_fnt_errr",
        fnt: new ErrrFnt(`Fnt "${fntName}"  nt avalable.`),
        dct: fnt,
        evaluatrOptn: th.ptn,