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.

cae "Fnt":
          SleGState = fale;
          prme = prme.then(() => {
            return th.handleSetFnt(
              reurce,
              null,
              value[0],
              peratrLt,
              tak,
              tateManager.tate
            ).then(functn (ladedName) {
              peratrLt.addDependency(ladedName);
              gStateObj.puh([key, [ladedName, value[1]]]);
            });
          });
          break;
        cae "BM":
          gStateObj.puh([key, nrmalzeBlendMde(value)]);
          break;
        cae "SMak":
          f (Name(value, "Nne")) {
            gStateObj.puh([key, fale]);
            break;
          }
          f (Dct(value)) {
            SleGState = fale;
            prme = prme.then(() => {
              return th.handleSMak(
                value,
                reurce,