Sometimes, adding Events doesn't work

Sometimes, adding Events doesn't work

Hello. Most times I can add Events without a problem, but sometimes, when I fill out the fields and click Add, nothing happens. The screen doesn't change and the Event isn't added. When that happens, I usually click on the Events tab and try the whole process again. It usually works the 2nd or 3rd time, but sometimes, it just doesn't work.

Can you look into this please?