In my installation the campaigns show the correct numbers in view period=month. When I switch to period=year it only shows the aggregated numbers for June and July, nothing before that.
At the beginning of June I installed the plugin MarketingCampaignsReporting, so the problem might be related?
I already tried invalidating the dates and recalculating the data (How do I tell Matomo to invalidate the past historical reports so they can be re-processed from the logs? FAQ - Analytics Platform - Matomo), but that did not help.