Someone had similar problem and updating firmware sorted it out.
I remember on some F5 the IR sensor was misalligned and some resorted to external usb IR sensor to sort the problem.
The main problem with this can be one of the terminals, its very tight and one of the batteries does not seat in properly and ive noticed this on 75% of skyboxes. Take the batteries out, re-seat them on terminals making sure to give the a slight push across then down to seat fully.