Xiao-nrf54l15 An error occurred: Memory transfer fault @ 0x00ffc31c-0x00ffc31f

The error message is from when the upload failed via USB. Comparing the error messages, it seems you’re in exactly the same situation. After that, I tried connecting JLink to the pads on the back of the board to perform a bulk erase for verification, but I couldn’t connect.

Were you able to recover?