Campaigns and period=year show wrong numbers (possibly related to plugin MarketingCampaignsReporting)

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.

Any ideas?