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[117] = 236;
  t[118] = 238;
  t[119] = 239;
  t[120] = 241;
  t[121] = 243;
  t[122] = 242;
  t[123] = 244;
  t[124] = 246;
  t[125] = 245;
  t[126] = 250;
  t[127] = 249;
  t[128] = 251;
  t[129] = 252;
  t[130] = 8224;
  t[131] = 176;
  t[132] = 162;
  t[133] = 163;
  t[134] = 167;
  t[135] = 8226;
  t[136] = 182;
  t[137] = 223;
  t[138] = 174;
  t[139] = 169;
  t[140] = 8482;
  t[141] = 180;
  t[142] = 168;
  t[143] = 8800;
  t[144] = 198;
  t[145] = 216;
  t[146] = 8734;