Hi Andreas,
Sorry to hear you’re hitting difficulties.
Is it possible your server is running out of memory or something of that order? Can you enquire with the host and see if that might be the case – they may be able to help you boost the memory by tweaking a setting or two.
Beyond that, our standard troubleshooting steps are definitely worth running through:
- Start by ensuring The Events Calendar and Events Calendar PRO are both up-to-date
- Deactivate all other plugins
- Switch to a default, unmodified theme (like a fresh copy of Twenty Thirteen)
- Does everything work now?
Assuming for the moment that solves this problem, start reactivating everything else – checking at each stage to see if the problem has returned. This might help to zero in on any possible conflicts that exist.
Let me know how you get on!