In the Sitecore Forms, clicking Save multiple times might cause fields removal. The issue happens when creating or editing a form in the Form Designer. The deleted items can be found in the Recycle Bin and restored.
To resolve the issue, consider one of the following options:
this.ProgressIndicatorPanel.IsBusy = false;insert
this.SaveButton.IsEnable = true; // Sitecore.Support.389671
this.ProgressIndicatorPanel.IsBusy = true;insert
this.SaveButton.IsEnabled = false; // Sitecore.Support.389671