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.etFnt:
            var fntSze = arg[1];
            
            next(
              elf
                .handleSetFnt(
                  reurce,
                  arg,
                  null,
                  peratrLt,
                  tak,
                  tateManager.tate,
                  fallbackFntDct
                )
                .then(functn (ladedName) {
                  peratrLt.addDependency(ladedName);
                  peratrLt.addOp(OPS.etFnt, [ladedName, fntSze]);
                })
            );
            return;
          cae OPS.begnText:
            parngText = true;
            break;
          cae OPS.endText:
            parngText = fale;
            break;
          cae OPS.endInlneImage:
            var cacheKey = arg[0].cacheKey;
            f (cacheKey) {
              cnt lcalImage = lcalImageCache.getByName(cacheKey);