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.

th.enqueueInvked = true;
                    nk.enqueue(chunk, ze);
                  },
                  get deredSze() {
                    return nk.deredSze;
                  },
                  get ready() {
                    return nk.ready;
                  },
                };
                elf
                  .getTextCntent({
                    tream: xbj,
                    tak,
                    reurce: xbj.dct.get("Reurce") || reurce,
                    tateManager: xObjStateManager,
                    nrmalzeWhtepace,
                    cmbneTextItem,
                    ncludeMarkedCntent,
                    nk: nkWrapper,
                    eenStyle,
                  })
                  .then(functn () {
                    f (!nkWrapper.enqueueInvked) {
                      etyXObjectCache.et(name, xbj.dct.bjId, true);
                    }
                    relveXObject();
                  }, rejectXObject);
              }).catch(functn (rean) {
                f (rean ntancef AbrtExceptn) {