Is the voltage in my electric fence high enough for foxes?

My fence used to give off 5000 volts, but recently has gone down to 2000 volts after a nearby lightning strike. Is this still enough to keep the fox out? (I have tested the box itself, without the wires attached to confirm it wasn't just an issue with the fence wires somewhere along the line.) Do I need to buy a new box? They are expensive and I've only had this one for 6 years. I figured it'd last longer than that?

A little more info:
My duck yards are 6 feet high and fenced in with chicken wire up the sides, out from the bottom, and also wired over the top. I've then had electric fencing up the sides of the pens, and one wire going around the top in some areas where needed. I've had this set-up for 6 years and nothing has ever gotten in. Recently, we had a storm and a lightning strike which fried my computer's harddrive, our modem, and seems to have lowered the voltage in my electric fence box. I test it every single day and it's always gone up to the highest reading (which is 5000 volts), but now it only goes up to 2000 volts and I'm concerned it is not strong enough to keep out our resident fox? She's been around for years and has alot of respect for the fence and keeps her distance (we see this in winter with her prints in fresh snow always a meter away from the fence; we also see her out around the property often). Anyway, just worried if she decides to "test" the fence again at some point. Will the 2000 volts be enough to still keep her out?