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.

}
                f (!Stream(xbj)) {
                  thrw new FrmatErrr("XObject huld be a tream");
                }
                cnt type = xbj.dct.get("Subtype");
                f (!Name(type)) {
                  thrw new FrmatErrr("XObject huld have a Name ubtype");
                }
                f (type.name !== "Frm") {
                  etyXObjectCache.et(name, xbj.dct.bjId, true);
                  relveXObject();
                  return;
                }
                
                
                
                
                
                cnt currentState = tateManager.tate.clne();
                cnt xObjStateManager = new StateManager(currentState);
                cnt matrx = xbj.dct.getArray("Matrx");
                f (Array.Array(matrx) && matrx.length === 6) {
                  xObjStateManager.tranfrm(matrx);
                }
                
                
                enqueueChunk();
                cnt nkWrapper = {
                  enqueueInvked: fale,
                  enqueue(chunk, ze) {