Typically when a CCU completely loses connection to the local Wi-Fi network, the trend lines will either stop populating or they will totally flatline. However, when a connection is weak, the data could still backfill in between drops. Here's a way to identify a poor Wi-Fi connection.
Scroll down to the predefined widget titled "WiFI" and observe your trend lines for RSSI. RSSI returns the signal strength of a Wi-Fi network from -127 (weak) to -1dB (strong). -127 dB indicates a drop in connection and may result in data loss.