2 units dropped out at same time

Here’s a minor anomaly, just curious if anyone has an idea of what might cause this.

I have two 100% reliable IoTaWatts in my panel. Last month I noticed that that I couldn’t access either unit so cycled their power (they’re on their own breaker inside the panel). They popped right back to life as if nothing had happened.

But it turns out that they had both stopped recording at the same time just over a week before:

I don’t see any telltale information in either log (below). Unless their breaker has a really weird failure mode, they both had power during this time.

Here’s a closeup of when they stopped recording:

Disclosure: both are on a single USB charger, which I promise to fix the next time I need to open up that panel.

Could a brownout cause 2 IoTaWatts to disappear and not come back? Maybe there’s some way to cause them to freeze until power cycled?

It hasn’t happened since. Other than this minor incident, they’ve been stone cold reliable.

Iota1 Logs
3/03/23 13:28:53 historyLog: service started.
3/03/23 13:28:53 historyLog: Last log entry 03/03/23 13:28:00
3/03/23 13:28:53 WiFi connected. SSID=iota, IP=192.168.1.11, channel=10, RSSI -40db
3/03/23 13:28:53 Updater: service started. Auto-update class is MINOR
3/03/23 13:28:54 Updater: Auto-update is current for class MINOR.
3/18/23 11:07:14 WiFi disconnected.
3/18/23 11:07:16 WiFi connected. SSID=iota, IP=192.168.0.101, channel=10, RSSI -40db

** Restart **

SD initialized.
3/28/23 22:37:49z Real Time Clock is running. Unix time 1680043069 
3/28/23 22:37:49z Reset Reason: Power-fail restart.
3/28/23 22:37:49z ESP8266 ID: 15931907, RTC PCF8523 (68)
3/28/23 22:37:49z IoTaWatt 5.0, Firmware version 02_08_02
3/28/23 22:37:49z SPIFFS mounted.
3/28/23 16:37:49 Local time zone: -7:00, using DST/BST when in effect.
3/28/23 16:37:49 device name: Iota1
3/28/23 16:37:52 Connecting with WiFiManager.
3/28/23 16:40:00 Did not connect after power-fail. Restarting to reset WiFi.

** Restart **

SD initialized.
3/28/23 22:40:02z Real Time Clock is running. Unix time 1680043202 
3/28/23 22:40:02z Reset reason: Software/System restart
3/28/23 22:40:02z Trace:  11:5, 11:10, 11:15, 11:20, 11:20[1], 11:20[2], 11:20[3], 11:21, 11:22, 11:21, 11:22, 11:20[4], 11:20[5], 11:20[6], 11:20[7], 11:25, 11:30, 11:30[1], 11:30[2], 11:31, 11:31[1], 11:31[2], 11:31[3], 11:30[3], 11:35, 11:36, 11:35, 11:40, 11:45, 11:50, 11:55, 11:70
3/28/23 22:40:02z ESP8266 ID: 15931907, RTC PCF8523 (68)
3/28/23 22:40:02z IoTaWatt 5.0, Firmware version 02_08_02
3/28/23 22:40:02z SPIFFS mounted.
3/28/23 16:40:02 Local time zone: -7:00, using DST/BST when in effect.
3/28/23 16:40:02 device name: Iota1
Iota2 Logs
3/03/23 13:30:20 historyLog: service started.
3/03/23 13:30:20 historyLog: Last log entry 03/03/23 13:29:00
3/03/23 13:30:20 Updater: Auto-update is current for class MINOR.
3/18/23 11:07:14 WiFi disconnected.
3/18/23 11:07:16 WiFi connected. SSID=iota, IP=192.168.0.100, channel=10, RSSI -30db

** Restart **

SD initialized.
3/28/23 22:37:00z Real Time Clock is running. Unix time 1680043020 
3/28/23 22:37:00z Reset Reason: Power-fail restart.
3/28/23 22:37:00z ESP8266 ID: 14646716, RTC PCF8523 (68)
3/28/23 22:37:00z IoTaWatt 5.0, Firmware version 02_08_02
3/28/23 22:37:00z SPIFFS mounted.
3/28/23 16:37:00 Local time zone: -7:00, using DST/BST when in effect.

If they are also both on the same AC reference as well, that is a big problem that should be rectified immediately. Also, when you say both on the same USB charger, you imply it is a charger rather than a power supply. The quality of charger power can cause problems as well. Obviously it is something shared by both units, so the USB and AC are suspect, as is the WiFi.

EDIT: From the logs it looks like that USB power supply stopped working. Get two independent switching power supplies.