How did the problem occur?
HOW STRONG IS THE LEAK????
CHANGE BATTERY!!!!
If the gun is leaking, where is the leak coming from?
And I mean, exactly.
Get the reg sleeve off if you can, then screw the reg back in and test.
Get a straw or similar and some really soapy (more Fairy than water) water and drop it in areas where you think the leak is (check with finger to see if you can isolate area, by feeling or quietening the leak), look for bubbles.
If no joy, semi disassemble the marker and then gas it up and check the banjo's etc with teh soapy water, or whatever...I haven't been too far into Epiphanys.