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[27] = 56;
  t[28] = 57;
  t[29] = 58;
  t[30] = 894;
  t[31] = 60;
  t[32] = 61;
  t[33] = 62;
  t[34] = 63;
  t[35] = 64;
  t[36] = 65;
  t[37] = 66;
  t[38] = 67;
  t[39] = 68;
  t[40] = 69;
  t[41] = 70;
  t[42] = 71;
  t[43] = 72;
  t[44] = 73;
  t[45] = 74;
  t[46] = 75;
  t[47] = 76;
  t[48] = 77;
  t[49] = 78;
  t[50] = 79;
  t[51] = 80;
  t[52] = 81;
  t[53] = 82;
  t[54] = 83;
  t[55] = 84;
  t[56] = 85;