Go to the Genre node in the "Entire Library" collection in the Media Tree.
Do you see just a single entry for the Xmas genre?
Maybe you have a typo somewhere, like a leading or trailing blank? Or some small difference that is difficult to notice.
Yes some relatively minor bugs ... especially in the beta releases. Nothing too destructive.
The issue is that MM has a wide scope of excellent features, at a modest price.
I have not seen discussion of any other software with such a full feature set, even at a greater purchase price.
And they usually do a good job of fixing bugs, once you get past the (sometimes difficult) hurdle of proving that there is a problem.