Mautic performance issue with dashboards

Your software
My Mautic version is: 2.15.3
My PHP version is: 7.1.33

Your problem
My problem is:

I have a performance issue loading mautic statistics into dashboards. The problem happens right after login and it takes 25 seconds to load the main dasboard, but the biggest problem is when I open the statistics of the biggest campaign that lasts 3 minutes to load. The statistics for this campaign are huge, with over 1 million shots for certain events. Looking at the performance of the servers I see a heavy use of mysql and started tuning the cache and buffer variables, but without much improvement, I’m running a 16 GB RAM / quad core server just for mysql.

These errors are showing in the log:

https://gist.githubusercontent.com/JoaoPauloSouza/eb9af33f4526f87cd136d79516dd0c47/raw/b41843c526db0abd6a4a18c6ddbab6b3a03e5e68/mautic.log

Steps I have tried to fix the problem:

tunning mysql and php config variables, clear cache, run mautic cleanup maintenance cron job