If the lights flash, it's very likely the air compressor (one for each diff) is running continuously. So, a leaky air line.
In the driveway, engage the rear locker, pop your head behind the tcase, the pumps are on a little tray bolted to the skid plate, behind the tcase.
Take a spray bottle of windex, save the windex, fill with water, and a little bit of sunlight dishsoap, shake, and spray soapy water on the airlines, compressor, and connection to diff. If you see growing bubbles, there is your leak.
Or, and it's a known problem, the pump body isn't all that serviceable, the body is plastic. The nipple that the airline connects to could be broken off. If the lights on the dash are flashing, are your lockers actually engaging? To test, put one side of the axle on a jackstand, engage the locker, you shouldn't be able to turn the lifted wheel. Hand turning the wheel wont engage the limited slip in the rear.
The two pumps have their rubber hoses running to the diffs, there is a blowoff line that T-'s into the other pump body as well. Four bolts hold the tray down, and the tray can be pulled down, and there is barely enough slack in the electric wires and hoses to visually inspect.
There is also an electrical two-wire connection at the diff, the signal from the dash turns on the pump, and shuts off the pump when the circuit is closed in the diff when the locker is engaged.
Mud can play havoc in that area behind the tcase, and at the diff connections. Both electrical and pneumatic.
Good luck, the air hoses are an odd size, but the pumps themselves are a little lax in the quality dept. And they are expensive to replace. Hopefully the pumps are sound, and it's just a simple fix for you. Good luck!
For what it's worth, I have a leaky front hose, and the pump runs semi-continuously. Since I engage the front so rarely, I'm not all that concerned about it.