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[797] = 64336;
  t[798] = 64337;
  t[799] = 64342;
  t[800] = 64343;
  t[801] = 64344;
  t[802] = 64345;
  t[803] = 64362;
  t[804] = 64363;
  t[805] = 64364;
  t[2424] = 7821;
  t[2425] = 7822;
  t[2426] = 7823;
  t[2427] = 7824;
  t[2428] = 7825;
  t[2429] = 7826;
  t[2430] = 7827;
  t[2433] = 7682;
  t[2678] = 8045;
  t[2679] = 8046;
  t[2830] = 1552;
  t[2838] = 686;
  t[2840] = 751;
  t[2842] = 753;
  t[2843] = 754;
  t[2844] = 755;
  t[2846] = 757;
  t[2856] = 767;
  t[2857] = 848;
  t[2858] = 849;
  t[2862] = 853;