[psy_wombats]

If you're taking values incorrectly from the IR sensor, the fourth may be the last one being updated. The IR sensor returns zero if a button is hit and 1 if it is not. 0 is also the unattached value. I suggest first posting your code or shuffling the order of your ifs/cases and see if another button is being triggered. If the fourth button still triggers, your sensor may not be wired right.