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.

t[3161] = 588;
  t[3162] = 589;
  t[3165] = 891;
  t[3166] = 892;
  t[3169] = 1274;
  t[3170] = 1275;
  t[3173] = 1278;
  t[3174] = 1279;
  t[3181] = 7622;
  t[3182] = 7623;
  t[3282] = 11799;
  t[3316] = 578;
  t[3379] = 42785;
  t[3393] = 1159;
  t[3416] = 8377;
});
/
/
/
const getSupplementalGlyphMapForArialBlack = getLookupTableFactory(function (
  t
) {
  t[227] = 322;
  t[264] = 261;
  t[291] = 346;
});
/
/
/
const getSupplementalGlyphMapForCalibri = getLookupTableFactory(function (t) {