Wix is honestly becoming a joke. God knows how long this has been happening, it wasn't until I began investigating increase in bounce rates I discovered this.
The lack of essential features for what they sell as an e-commerce solution and "a builder without limits" is fraught with errors, random and consistent, and restrictions, and lack of standard essential features. And one of the worst and slowest editors available.
They shouldn't be able to miss-sell and act like this!
Ok so it seems a random error. After monitoring and refreshing/revisiting over and over its intermittent. Keep your eye on your stores through Firefox and report if you see the issue too.