In my SonarQube project I’ve set my leak period to 2020-12-01 and I get 43 smells in the “Issues” page.
However if I instead filter issues manually since the same date, I get 2 more smells, which I think are legit as they were detected on 2020-12-9. One of them is shown in the following snapshot:
SonarQube v7.2 has been EOL since… August 2018 (when SonarQube v7.3 was released). You really need to upgrade to v7.9 LTS and then v8.9 LTS (currently the minimum supported version of SonarQube).
A lot has changed since then, such as how new code is detected and when issues are backdated, along with thousands of bugs fixed + improvements added.
Furthermore, since SonarQube v8.0, setting a specific date as a Leak Period (now called New Code Period) is no longer supported, now instead you select a specific analysis (this is all handled automatically in the upgrade migrations).
If you still face the issue after upgrading and triggering a fresh analysis, feel free to come back to us. Unfortunately, we won’t be able to provide any help until then.