Hi Simone,
I realize you have had a few open threads recently so you may already have run through our usual troubleshooting steps – but basically I’m wondering if this issue is directly tied to your theme (Gantry) or if you’ve isolated the problem to some other component?
If you know that the problem only occurs with Gantry, can you confirm if you have additionally tested it out with just Gantry, The Events Calendar, Events Calendar PRO and no other plugins and does the same issue occur then?
Thanks for confirming 🙂