Event Form not Saving

Hi all, please I’m having issues saving one of my event forms. After filling the form and clicking any of the save buttons, nothing happens. I’ve checked the console and application section of the dev window, but no error. This form has been used multiple times in the past month, it just sopped saving all of a sudden.
All my other event forms get save successfully. What could be the problem?

Thanks in advance!

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@Gassim @Ulanbek Please your help and suggestions would be appreciated.

@Rae send me private message with piece of your code and the screen shots with server response.