The DL4 is awesome but those switches are absolutely terrible!
When my dads DL4 died, I managed to fix it by replacing the stock switches with these ones from Small Bear...
Http://www.smallbearelec.com/Detail.bok?no=672
Or it might have been these...
Http://www.smallbearelec.com/Detail.bok?no=26
Either way, you just need to remove both parts of the stock switches (open it and you'll know what I mean) and solder wires from the two lugs on the new switch (in the above links) to two of the holes (left from the removed stock switch) diagonally across from each other.
Test it before soldering it in place and make sure that the wires you use are long enough to let you put the PCB and new switches back into the case. It's a VERY easy job and is well worth it to save an otherwise fairly busted pedal. I'm pretty hopeless with a soldering iron and I had no problems. I swapped out the LEDs for orange ones while I was at it.
Flick me a PM if you need any more info
Hope that helps.