Same issue here Michael. I have a support ticket in. It has been escalated and I’m waiting to hear back from WiX Support.
For me, it started about a week ago. I can create submit buttons and they will work, but attempting to change the Success or Error text boxes does not work. On top of that, I lose the ability to drag any text box elements around my page until I reload the Editor.
I trust the kind folks at WiX are working on a fix.