First off, check all the component values, and orientation of diode and electrolytic caps - it's easy to plop something in backwards.  If all that checks out you might consider the Transistors - are they within the correct gain range?  If you've bought pretested tranny's you don't have to worry so much about this.  The 172's should work in place of the 127's - as I recall they are similar in their specs.  Are the tranny's good?  Have you tested them for leakage and gain?  Germanium transistors by their nature are prone to failure.  Here's a link for testing bi-polar trannys (NPN or PNP) - 172's are NPN. 

http://www.anatekcorp.com/qdmmvom.htm

This will only tell you if they are good/bad - won't help you measure gain(hfe).

Here's an article by RG Keen over at geofex that details everything you need to know about the fuzzface circuit(which is very similar to benders). 

http://www.geofex.com/Article_Folders/fuzzface/fftech.htm

It details a method of testing PNP trannys for gain and leakage - this setup can be modified to measure NPN's but I can't walk you through that - I rarely use Ge NPN's so I never test them.  Have you looked over at http://diystomboxes.com forum?  Someone there will surely know the testing method.

Hopefully my ramblings will give you a few places to search further.