problems with xfinity dvr and samsung tv picture shrinking

I have a new Samsung S95B TV attached to an Xfinity X1 DVR box. Every few days when the TV is turned on the picture shrinks to the upper left corner of the screen and the only solution is to restart the box. Any ideas as to a setting to correct this problem? When I spoke with Samsung they had me check if a streaming program did the same, and it did not. It only shrinks when it is using an Xfinity channel.