Thank you for your response. I have 300 events in the system – it is not many, but as I said – few events before there were no errors.
Yes, I was talking about memory_limit – my web host will not allow me to expand this value at this moment.
The plugin would be the best solution, but in order to activate it, I have to get into plugin settings, but there is an error occured, when I try 🙂
Do you know how to find the meta data in the database, connected with the removed events?