Comparator doesn't give an output from a item frame if a button exist in the same block.

If a button exist in the same block as the item frame a comparator won't read the item frame's output.
Steps
1.) place button (any orientation works)
2.) place an item frame in the same block as the button
3.) place a comparator to try and read the item frame"s output
and that's all the comparator won't read the item frame ONLY if the button is placed first.