Had a super humbling and awesome experience over the past few days regarding the low-profile Keychron K5SE. My version was the RGB backlit one with hot-swappable Keychron optical switches (I chose the mint switches).
So I originally got it on Monday, and was super excited to try it out after work. When that time came, I typed on it a little bit, but didn't like how rattly sounding the stabs were, so I took everything apart to lube the stabs (decided to lube the switches as well, because why not?). After lubing everything, I wanted to also throw in a thin layer of PE foam that came with the box, because I figured it would be nice to fill in the space between the bottom case and the PCB. I also figured I'd try out the Tempest tape mod, which is basically applying layers of non-conductive carpenter's/painter's tape on the back of you PCB to make the sound when typing more "poppy".
Well, I put everything together, realized there wasn't enough room for both a foam mod and a tape mod, took out the tape mod, and... the keyboard didn't work.
The LEDs and RGB lighting all worked, but no keys actually responded to my presses.
So, I spent the next few days researching and asking for help on r/BudgetKeebs and was pretty bummed out about the whole ordeal. My very first keyboard that I took apart and modded and I broke it!
As I was finishing up work today, I got a response from someone on r/BudgetKeebs who told me to look for a reset switch under the spacebar area on the PCB as Keychron keyboards sometimes have this switch. I reluctantly opened everything back up again and was sad to see that there was no switch. However, there was some weird yellow residue and some tape residue from the tape mod (at this point, I just took out the foam as well because I thought bringing everything back to a stock version might've helped).
Without hoping for anything, I used a cotton swab with isopropyl alcohol and cleaned the yellow residue along with the PCB overall.
Popping the battery connector in, I put a few switches into the PCB to test the keyboard and... IT WORKED!
Cleaning the PCB from the residue and whatever grime was on there totally fixed my problem and I was so happy! I learned that sometimes, you have to start from the ground up when troubleshooting and in my case, it was making sure that the PCB was clean. I had thought that I fried my PCB because my painter's tape had some sort of conductive acrylic, but it was just a matter of making sure that the PCB was clean.
Anyways, I'm going to put the foam back in there tomorrow and see how everything sounds and feels. The stabs are WAY better after lubing them, and I'm pretty happy with the mint switches (a tactile copy of the holy panda switches). So far, I'm liking the keyboard for a low profile tactile typing experience. I'll be using it interchangeably with my other work keyboard and am looking forward to when my V1 arrives to mod that as well if need be!
Pictures were uploaded to my Imgur here.