Someone plotted test result IDs and times and the outlier is Djokovic's positive test - https://twitter.com/msuvakov/status/1481018537368035330

From the whole timeline, it would look to me as someone created a later test result that they backdated for him to be able to apply for a Visa. This would explain why Djokovic was out in public at the time he was apparently positive (I doubt he would have public appearances after a day after a positive test) and it would explain the test result ID discrepancy.

It could also explain why the positive test result was generated on 26th and the negative one on 22nd.