Shruthi LED3 not lit

I’d been putting off ordering a Shruthi or Shruthi XT for a while, but I got a bit of a stipend from my first research grant shortly before I saw that Olivier was going to stop selling the kits and I immediately ordered one. It’s been a fun little project to work on between classes this summer, but it’s also the first time I’ve soldered anything so I’ve made a couple mistakes so far (that I’m aware of). Initial tests of the power supply circuit on the filter board looked good so I proceeded to build the rest. Unfortunately, having reached the point where I could connect the two boards and test the LEDs, I’ve discovered that LED3 appears unresponsive.

Here’s a picture of what’s going on when I power up the control board:

Turning the encoder knob produces a shifting pattern of on/off LEDs that I assume is normal, only LED3 appears to be a problem.
Having never built anything like this before I just used what I had available, which was the 25W weller soldering iron my dad used as a kid and described as being old when he got it in the 60s This was making things frustratingly difficult, so I picked up a variable temp iron off of amazon. So far, I’ve only used that to add the buttons. Hopefully the old iron I was using didn’t cause any problems that can’t be fixed. Being so new at all this I’m not sure what to even check to determine what is causing the LED problem and I’d be immensely grateful for any troubleshooting help you guys can give me.

The only other potential issue that I’m aware of is the Q1 transistor on the filter board. I accidentally put it in backward and tried to desolder it, flip it around, and resolder it in the right orientation. I realize now that I should have just cut it off and put in a replacement but at the time I just did it the hard way and I’m afraid it may have been overheated or damaged by the pliers I used to try to pull it out. If it doesn’t work now, I’m not actually sure how I’d cut the leads off since it’s packed in between other nearby parts. Other than that, the only other deviation from the instructions was simply having to order another 4.7u capacitor (my bag had an extra 100u and one too few 4.7 - no big deal, I can see why Olivier would get tired of managing all these kits) but I used the part number off of the BOM included in the instructions so I’m assuming that’s fine. I ordered an extra transistor too, in case I need to replace that.

I put some build pics up on imgur - I tried to take clear pictures of everything but if there’s something I missed just let me know. The boards get a bit of sawdust on them while sitting around, but I blow that off before soldering anything.

On a scale from 1 to 10… how completely have I screwed this up?

Try reflowing the solder joints on the 595. Also, are you sure that the polarity of this LED was correct?