There seems to be an issue with one of the 2N3904 transistors in this build. Please see BYOC's note below and act accordingly.
There seems to be a problem with the use of the 2N3904 transistor in the Q2 (transistor closest to the BBD) position. For whatever reason, the circuit seems to prefer seeing a higher gain transistor here. Do you happen to have any 2N5088 or 2N5089 transistors laying around? If not, please contact
sales@buildyourownclone.com and we'll send you one.
To remove the old 2N3904, do not bother trying to desolder it. Just clip the leads. Then heat up the solder joints and pull the legs out of the eyelets with pliers one by one. Once you have removed the old transistor, you can desolder the eyelets. It's much easier this way, and less risk of damaging the PCB. If you're using desolder braid, I recommend added a tiny bit of fresh solder to the old solder joints before desoldering. It may seem counter intuitive to add more solder when you're trying to remove the solder, but the fresh flux helps the old solder wick better.