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[116] = 87;
  t[121] = 88;
  t[122] = 89;
  t[124] = 221;
  t[127] = 90;
  t[129] = 381;
  t[258] = 97;
  t[260] = 225;
  t[268] = 261;
  t[271] = 98;
  t[272] = 99;
  t[273] = 263;
  t[275] = 269;
  t[282] = 100;
  t[286] = 101;
  t[288] = 233;
  t[290] = 283;
  t[295] = 281;
  t[296] = 102;
  t[336] = 103;
  t[346] = 104;
  t[349] = 105;
  t[351] = 237;
  t[361] = 106;
  t[364] = 107;
  t[367] = 108;
  t[371] = 322;
  t[373] = 109;
  t[374] = 110;
  t[381] = 111;