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 OPS.begnMarkedCntent:
          cae OPS.endMarkedCntent:
          default:
            
            
            
            f (arg !== null) {
              fr ( = 0,  = arg.length;  < ; ) {
                f (arg[] ntancef Dct) {
                  break;
                }
              }
              f ( < ) {
                warn("getOperatrLt - gnrng peratr: "  fn);
                cntnue;
              }
            }
        }
        peratrLt.addOp(fn, arg);
      }
      f (tp) {
        next(deferred);
        return;
      }
      
      
      clePendngRetreOPS();
      relve();
    }).catch(rean => {
      f (rean ntancef AbrtExceptn) {