Apologies, i meant to respond a bit sooner. I have had contact with a support engineer who seemed very knowledgeable about the matter. I was offered to return the devices and have them replaced. As i did not expect the replacements to be free of this reset issue, and patching a wire across the normally open contacts of the relay fix the resets quite as well (i primarily wanted power measurements), i did not push for returning. I did offer to return them if they wished to specifically research my devices in order to find the general problem to improve the product. Also i noted that it might be related to the method of use, as my homebrew application depends on the app interface.

At this point (the return offer, and tp-link verifying the pruchase receit as being legitimate), communication from tp suddenly stopped. No mails were answered by tp-link from that point onwards. I would have preferred a more definite end to the interaction, even if it were just a confirmation to not support any further.

@jvgfg same issue here with random on/off/on... (but no off/on/off randomness). I discovered the issue in about thirty minutes.  This is not related to bad switches or circuits but rather to the LAN on which the smart switches reside.  I have ten switches six of which are in the same room on various circuits.  They would all cycle on/off/on randomly but in unison within a minute or so.  This behavior pretty much ruled out switches, sockets or plugs.  I have approximately twenty video servers (IP cameras) running constantly on my LAN and have seen this sort of random behavior from other non related devices also on the same LAN. Some of the less expensive servers have been known to 'malfunction' and create 'noise' on the LAN which can have undesirable impacts on the properly functioning devices.  This has occurred a couple of times over the past year for me. In this case it was an AmCrest dome camera malfunction that was resolved with a simple reboot.  No more switch cycling.  A previous occurrence similar in nature however unrelated to the smart switches was created by a different brand IP cam.  Again, a simple reboot cured the issue for other devices on my LAN.