JCC One For the Sky Satellite Equipment Tech-Savvy

I have an old Panasonic Sky Box - model TU-DSB30. It's ancient but serves its purpose. I've had problems in the past with it freezing and have managed to get it going again by powering off/on while holding the backup button down til the 4 lights show on the front. So far so good. The problem seems to be endemic with older boxes of this particular model. Point is, so far if it freezes I can fix it.

Recently (like within the last couple of weeks) the box has started freezing at just after 5:30 PM every day. Picture just freezes, no buttons work, I have to go through the reset procedure described above. Now. I'm normally watching the TV at this point because Doctor Who reruns are on. I thought maybe it was heat-related so I've kept the box unplugged (i.e. not in standby) til it's needed. Today I plugged it in and put it on just before 5PM. At 5:33 PM - freeze. Box wasn't what I'd call hot to the touch.

The box lives at the top of a stack comprised of an Echostar free-to-air box with positioner used to swing the motorized dish. At the bottom of the stack is the VCR. None of this setup has changed in years. Nothing new has been added and I haven't been messing with wires, etc. I did some Googling about things freezing at a certain time of day but most of what I found was PC-related, not Sky Box related. I figured I'd ask here before phoning Sky as they will only want to send an engineer for around £65 for a callout..
I thought of electronic interference but at the time it happens no one is usually home in the building but me. I'm stumped. Any ideas?