Two out of five of these died, but I managed to repair both of them, so here's a report to warn others about the quality, usage, and give some guidance for fixing them in case you already have them. I have the EU version of the ESPHome flashed plug. I ordered 3 times from Athom's AliExpress site so far:
- 2021-12: 2x original version: [1] power for my 3d printer, most of the time in the OFF mode, [2] washing machine, was always ON, used for notification when the washing finished based on power consumption
- 2022-03: 2x original version: [3] used for an espresso machine (ON for about 20 minutes a day), [4] desktop PC, always ON, used for power consumption reports
- 2022-09: 1x version 2 (more accurate): [5] replacement for [4]
Plug [4] died first after a power outage, it never turned back on, got hot and never showed up on WiFi. This happened just after 6 months of usage.
Plug [2] died just a few days ago after a bit more than a year.
Both of these were the ones that were always ON. This was a good clue for the repair.
Disassembly
I found this similar looking plug and followed the disassembly instructions: Damage free disassembly of an BSD33 EU Smart Plug | Blakadder's Smarthome Shenanigans -- for me it definitely was not damage free. The case of these Athom plugs seem ultrasonically welded, and took some force to crack them open and the pipe wrench left a lot of teeth marks. I also slightly cracked the plastic here and there, but it's not a structural or safety issue.
I reassembled it with hot glue around the edge to make it easy to take it apart again if necessary. It would look better with superglue inside the ridge.
Repair
It was not too hard to notice that the low power capacitor went bad. Not sure if it blew up or just slowly expanded, but it was clearly dead. For reference it was a ShiCaXon brand, 10V rated, 470 uF capacity one.
I replaced it with a 16V 220 uF low-ESR (I did not have the proper capacity at hand), and the one I fixed 3-4 days ago works reliably since then and the one I fixed today seem to work as well.
I assume this capacitor is used for the step-down power transformer that runs the ESP chip and the relay, and it is either very low quality and/or probably not low-ESR which is necessary for surviving the rippling that these need to withstand from the AC source.
Neither of these broken plugs damaged the device plugged into them, they failed OFF, disconnecting the power. So that's good at least.
I think with this repair these plugs will keep working for a long time, but I will definitely not buy more. I suspect with less load on them (being ON rarely and not powering the relay) these would fail a lot later. Not sure if they made any changes on the "v2" version, but I definitely won't be buying more of them.
I hope this report is helpful. I wonder if they use the same components in the other plug types, and whether the refreshed version fixed this or they will keep failing after this cap dies?