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[2983] = 1551;
  t[2984] = 1552;
  t[2986] = 1554;
  t[2987] = 1555;
  t[2988] = 1556;
  t[2990] = 1623;
  t[2991] = 1624;
  t[2995] = 1775;
  t[2999] = 1791;
  t[3002] = 64290;
  t[3003] = 64291;
  t[3004] = 64292;
  t[3006] = 64294;
  t[3007] = 64295;
  t[3008] = 64296;
  t[3011] = 1900;
  t[3014] = 8223;
  t[3015] = 8244;
  t[3017] = 7532;
  t[3018] = 7533;
  t[3019] = 7534;
  t[3075] = 7590;
  t[3076] = 7591;
  t[3079] = 7594;
  t[3080] = 7595;
  t[3083] = 7598;
  t[3084] = 7599;
  t[3087] = 7602;
  t[3088] = 7603;
  t[3091] = 7606;