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.

if (nameEntry === part) {
                fallbackData = {
                  name: part,
                  header: potentialHeader,
                  tables: potentialTables,
                };
              }
            }
          }
        }
      }
      if (fallbackData) {
        warn(
          `TrueType Collection does not contain "${fontName}" font, ` +
            `falling back to "${fallbackData.name}" font instead.`
        );
        return {
          header: fallbackData.header,
          tables: fallbackData.tables,
        };
      }
      throw new FormatError(
        `TrueType Collection does not contain "${fontName}" font.`
      );
    }
    /**
     * Read the appropriate subtable from the cmap according to 9.6.6.4 from
     * PDF spec
     */
    function readCmapTable(cmap, file, isSymbolicFont, hasEncoding) {