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[2941] = 7495;
  t[2942] = 7496;
  t[2944] = 7498;
  t[2946] = 7500;
  t[2948] = 7502;
  t[2950] = 7504;
  t[2951] = 7505;
  t[2952] = 7506;
  t[2954] = 7508;
  t[2955] = 7509;
  t[2956] = 7510;
  t[2958] = 7512;
  t[2959] = 7513;
  t[2960] = 7514;
  t[2962] = 7516;
  t[2963] = 7517;
  t[2964] = 7518;
  t[2966] = 7520;
  t[2967] = 7521;
  t[2968] = 7522;
  t[2970] = 7524;
  t[2971] = 7525;
  t[2972] = 7526;
  t[2974] = 7528;
  t[2975] = 7529;
  t[2976] = 7530;
  t[2978] = 1537;
  t[2979] = 1538;
  t[2980] = 1539;
  t[2982] = 1549;