Replying to this old thread as I found it through search and experiencing the same issue.
I found a solution from this thread:
https://xdaforums.com/t/battery-usage-empty-no-usage-statistics-or-graph.4211131/
Changing the time and reverting back to the original time fixes the issue immediately for me. It seems I have to do this each time the stats are lagging behind.
Could this be an issue of a hardcoded timezone somewhere, confusing the statistics?