Why are my classes on the Check-in Family Page listed as Undefined?

Important check-in view custom setting caused this. Here's the fix.

In option E5 of a Check-in view if you remove the default background image by just deleting the URL as shown below it can cause an issue where UNDEFINED shows up instead of the group names. This happens because the code ends up refreshing the page looking for the image which messes with some important settings. If you delete these 3 lines this will be fixed.

background-position:center top;
background-repeat:no-repeat;
background-image:url(' ');