Probably your issue is that the aggregation is too agressive? you can change the aggregation into “Others” see faq at How to - Analytics Platform - Matomo
The aggregation isn’t too agressive, on Back-End is ok.
My Problem, I programming for my Webseite display Top-Ten of Downlowads of the year. When i musst wait befot XML full download zu parse then is not optimal. My workaround is once in the night full download with cronjob and parse the local xml File.