If I may add some thoughts to this discussion, I see that the supply voltage feeding the B. LEVEL pot will also determine the voltage at the LED in the VACTROL. If you have a weak battery, this may not provide as much light from the LDR in the VACTROL and, therefore, prevent some signal level from reaching IC1a.
In any case, as long as you can achieve unity level at the output, you have a perfectly usable pedal. I always believe it is best to maintain unity level throughout the signal chain on the pedal board unless you are trying to Boost the level going to the amp to overdrive the front end of the amp. Your thoughts, Cybercow?