When the new update was installed, the custom css class(s) field beneath the "Displayed header:" was broken. Upon investigating, we found table headers are being connected to the last word in the class with an "_" underscore.

For instance, we add the class "poll-table-class data" in that field and it is now appearing as "poll-table-class data_Date". 

If and when I remove "data", then it will return "poll-table-class_Date" instead. I erased several styles in our main stylesheet before I realized the update was the issue.

I've attached a screenshot to show you that all of those classes are attached to the element that follows, which of course breaks the style of the table. That particular class adjusts font-size and text-align.