This is a great thread, lots of information here on a good budget regulator. I recently got a brand new M957 for $60, but it came with a leaky solenoid, so I am planning on using it for a fishless tank system that will have 8 aquariums total hooked up to it. I too have had some problems adjusting the needle valve, its not that precise, but for the price it gets the job done. I wouldn't not suggest using this regulator on a tank with a bunch of expensive fish, but to have on hand as a backup or to use for fishless systems it would work amazingly.
Sounds like your doing what I am doing. I will be pulling my retired Milwaukee out and running it on (8) fishless tanks. I replaced mine with the electronic Aquariumplants.com regulator and it rocks. Until I can get another Aquariumplants regulator the Milwaukee will serve it purpose since it will only be aquascaped tanks for at least a year. I just hope it still works as it did before it was retired.
Glad I ran across this troubleshooting thread though. Only issue I actually had with this regulator as well as any with a solenoid I guess, is the dumping of the tank. I lost half my tank due to me missing my "time to refill" window. But I will definite use this thread if needed.