2 things.......
1. are your christmas albums filed under 'XMAS' folder? If not, that is your problem.
2. have you turned the 'XMAS' option 'off' under the settings menu within Videobox? If not, that is you problem.
I am guessing that it is the first one of these 2 that is causing you the problem. Make sure 'ALL' you christmas songs are in the XMAS folder otherwise they go into general circulation with the background music too. I had a couple of random christmas songs on 2 albums and I thought the same as you, but realised the mistake and moved them into the folder. Good luck.