EEG signal maxing out, all channels RAILED

I have an OpenBCI Ganglion board, and have closely followed the Getting Started guide (double checking the electrode placement). The impedance values for all four channels are < 30 kΩ. However, when running the data stream, there seems to be abnormally high amplitude, with the word RAILED showing up frequently in all four channels:

What can I change to improve the signal quality? Is this possibly a damaged device, poor reference electrode placement, or something else entirely?