Hey Philipp!
Sorry to see you’re having issues with the order of events displaying incorrectly. I see you said ‘Yes’ to deactivating all plugins other than ours, but you did not revert back to the default WordPress theme. Please review our Testing for conflicts guide and reply back with your findings. This is a required step to continue receiving support.
I notice in your System Information you have the Facebook Events and iCal Importer plugins installed on your site. If you’re not aware, we are in the process of retiring both of these plugins and replacing them with our newest plugin, Event Aggregator.
Please make sure WP_DEBUG and WP_DEBUG_LOG are enabled on your site’s wp-config.php file. Any errors will display at the top of your page as you try to reproduce the conflict. I also recommend right-clicking your mouse and opening the ‘Inspect’ tool to see if any errors display in the console. Note what you find and please include it in your reply.
You have been granted a license for Event Aggregator and it is set to expire on the same date your iCal Importer and Facebook Events licenses expire. For information, please review our Moving to Event Aggregator Knowledgebase article and if you run into any issues along the way, please create a separate thread.
Please let me know what you find after your testing and have a great rest of your day. Cheers!