Hello, New here. I have pretty much zero knowledge of electronics. I recently soldered this circuit for my ship lighting. It worked fine on my 9v battery, so I assumed it was ok. I then hacked up a DC power supply and plugged it in. The timing is now uneven and even has a weird double-flicker at the end. Happens on both circuits. I tried with multiple LEDs (with correct resistors) and also on a pre-resistored LED light strip. I also tried different power supply (12v). The flicker changes its pattern but it's still there. Any ideas on what the issue might be?