Hey there svlevchik; thanks for the note here, and my apologies for the fact you're faced with problems.
This definitely isn't the core behavior of the plugin, and I'm unable to recreate on my end...which makes me think something else could be at play here. Can you try updating an event and - before attempting to view it - flushing your permalinks? This means just going into Settings -> Permalinks and saving (without making any changes), then trying again on the frontend.
Give that a go and let me know if you're still having problems; I can try to troubleshoot as needed.