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[87] = 116;
  t[88] = 117;
  t[89] = 118;
  t[90] = 119;
  t[91] = 120;
  t[92] = 121;
  t[93] = 122;
  t[94] = 123;
  t[95] = 124;
  t[96] = 125;
  t[97] = 126;
  t[98] = 196;
  t[99] = 197;
  t[100] = 199;
  t[101] = 201;
  t[102] = 209;
  t[103] = 214;
  t[104] = 220;
  t[105] = 225;
  t[106] = 224;
  t[107] = 226;
  t[108] = 228;
  t[109] = 227;
  t[110] = 229;
  t[111] = 231;
  t[112] = 233;
  t[113] = 232;
  t[114] = 234;
  t[115] = 235;
  t[116] = 237;