pics of pcb, controller, etc....?
1. the simplest explanation is a bridge somewhere, making the switch look like it's depressed when it physically isn't. being that's it's probably 1st in the row/column, i'd start there. also check the controller, pins are spaced close there and easy to accidentally bridge.
2. pins used on microcontroller, i remember someone else having issues when one of their rows/comums was connected to one of the "INT" pins, can't remember if it was D2 or D3
![Help - Custom build QMK spewing 250543-0](https://geekhack.org/index.php?PHPSESSID=7hd6ge2s8cbeiql969mmoppp5hf5etjn&action=dlattach;topic=108369.0;attach=250544;image)
3. make sure your wiring is correct in kbfirmware.com, and everything is configured correctly in the pins tab
- post pics of pcb & controller, how you have it wired, etc.