Incorrect and inconsistent download statistics

I have mutiple issues regarding the download statistics:

  1. In a month where I know for sure that a file has been downloaded, the monthly statistic shows no download for this file, whereas the statistic on a weekly basis in the same time period shows the download.
  2. When I request the downloads for an entire year, the number of downloads shown is less than the amount of adding up the monthly downloads of the respective document in that year. I was told that Matomo only saves data up to 120 days regarding the annual statistics, but this does not seem to make sense if the data is available on a monthly basis. Might it be a bug that only 120 days are calculated for the annual statistic?
  3. Some of the download data that I saved before the Matomo 3.9.0 and 3.9.1 update is not consistent with the data for the same period of time that I retrieved just now. So far the number of downloads shown for some of our documents available for download is less than what was displayed in the beginning of March (before the update).

I would appreciate help and solutions very much!