This is a combination of the browser improperly filling in the data and the customer not finishing the CC data during Guest Checkout.
When I go to Guest Checkout and tell it my email, my Chrome browser will sometimes fill in extra data in the wrong place.
You can see that the city has been incorrectly added to the Street Address and Address Line 2.
You have no way of controlling this. This is the individual's browser doing it and their not checking the data before hitting Save Changes.
NEXT..........
Again, the customer uses their browser or some other means (Windows Hello in windows) to insert their credit card data.
In the example below, I've used a fictitious CC number but this is what it would look like after the browser has entered the data. Notice that the ZIP is not entered.
This is where most of the Token errors come from.
The customer has the browser load the CC data and sees the screen change. But, they don't see that the ZIP has not been filled in by the browser.
IF the customer clicks on Confirm Order with the Credit Card information looking like that above, they will get the token error mentioning a problem on line 261.
More often than not, the customer has the problem in BOTH areas but only fixes one. They will continue to get the error until they get frustrated and say, "I'll just start over". At that point, they are looking for something to blame you for but, generally, they finally find ALL the problems with the order entry and get a successful order.
The error will show up with a file size of 299 in the display logs:
PHP Notice: missing token result: check if card button is disabled on dev console using: document.getElementById('card-button'); else look for javascript error in console. in /includes/modules/payment/square_webPay.php on line 261
Notice the mention of 'card-button'. The individual hit the Confirm Order before making sure ALL the data was filled in.