dual voicing filter unit issues? cap values?

[Canucker]

So I put this together and it works fine for a few minutes then theres a pop and it stops working until I unplug a battery and plug it back in. The only thing I changed is where it called for 2uf caps I used 2.2uf caps...another thing...I put it in a large box so the wires I used are pretty long in some cases. I may have to scan the schematic because I couldn't find it online...which surprised me. Thanks in advance for any feedback.

[Canucker]

Its a project in the Craig Anderton book "Electronics Projects for Musicians" for anyone that was wondering!