Harbinger One 2015 signal issue

[dreamsinbinary]

I'm having a rather odd issue (or I'm hoping it's not odd and I'm just overlooking something), but finally got around to building this and everything SEEMS fine. I'm using 18v to power it and per the schematic I'm getting 18v and 15v off the regulator. Spot checks show proper voltages around the circuit. Not seeing any solder bridges or incorrect values.

Now what it's doing...
With nothing plugged into the input and the effect active; I either get a thud or a chirp (depending on chorus vs vibrato) in sync with the LED indicator and the bulb. Volume, Speed, and Intensity all affect this.

With incoming guitar, I get the same chirp or thud, but also a very degraded guitar signal mixed in. The guitar cuts in and out as the bulb blinks. Sounds almost as though the bulb is somehow acting as a VCA or gate.

Anyone experience anything like this before? It KIND of sounds like transistor problem to me, but not sure where to start.