Why is the break sometimes high and sometimes low

check fuses and connections --dead battery--

Good idea to bench test, whatever it is.
Low volts? What is the high volts?
Belt driven or electric compressor, what you choose to start up needs to make, break, and carry the load in amperes. Thermostat, relays, contactors, solenoids, inverter, transformers, coolant sensors.
It's sometimes chosen, more practical, to use a control circuit (low voltage), and a power circuit(high voltage), for controls and for power hungry consumer loads.

The dimmer switch on the turn signal stalk can be open, so that either the high beams, the low beams, or neither the high or low work. It requires a new turn signal switch, sometimes listed as a multifunction switch.

Find the break in the power wire for the low side. High beam works, ground is good. Low beam works on the other side, so you have power threw the switch and turn signal. Wires usually break close to the plug. Also check the plug for corrosion. White to a greenish color.

you might have the bulbs installed backwards. the bulbs have two elements a low and high. you might be seeing the low when you hit the brakes. if the bulbs are in or wired backwards you would not see the low to high difference if the were in backwards and the lights were on

Check the fuses. If both low-beams went out at exact same time, it is probably the fuse (hopefully not a wiring short).
If they went out with a couple days or weeks of each other, it could just be the bulbs. They typically have very close lifespans and if they were installed at the same time, could burn out near the same time.
If the fuse is good, take the bulbs out. Look for a break in the filament.
Sometimes a fuse can break right at the base and you can't see it and sometimes a bulb can burn out without breaking the filament. If you can't see a break in either, start by replacing the fuse. (You can even take a same sized fuse out of a non-vital electronic (maybe radio, or power windows) and put it in the low beam spot.) If they work, there's the problem. Replace the missing fuse and your good. If not, then replace the bulbs.

Return Vehicle to the dealership for service, there is a recall out for this problem unsure if this model is included but I would still return it to the dealership for immediate servicing.

do thr break lights work? sometimes people put the blinker bulbs in reversed and cause the low element to flash which will not be seen over the high element..oh and congrats on having the beast.im an evo owner

the switch shuts off compressor when its low on freon..try adding some

Check for headlight relay and fuse. Some cars have separate circuits for head light flasher and normal high/low beam. From your description, I would suspect a bad connection to/from relay or relay itself.