I have exactly the same problem with P110.  One failed, killing my internet/router while we were watching TV. Another one failed less than a week later (fridge out).  Now today, another failed (click-click-click).  All three were from the same batch, under six months old, and are 6-12 months older than a bunch in the house that are still working fine.

 I have six HS110s for over 3 years now. Because their form factor is quite bulky and often obscured the outlet next to them, I started buying KP115s when they became available, eventually buying six of them about two years ago. About half a year ago, the KP115 monitoring my fridge starting clicking off randomly. Unplugging and replugging fixed it but not long after it started clicking on and off in quick succession. Dead.

This morning I walk into my living room to the same clicking sound. I recognised it immediately, and yep, the one for my rear speakers is gone.

While I have a smaller sample size, my 1 in 3 failure rate is consistent with others in this thread. It's worth noting that none of my HS110s have failed and I've had them for even longer, which leads me to believe there's a flaw in the parts or design of the KP115 that allows them to be much more compact.

The one for my fridge was pretty much only monitoring energy usage. Since it's a fridge it doesn't really get turned on or off. The one for my rear speakers turn off when no one is home.

I replaced the fridge one with a different product but had been considering getting more Tapo ones now that Kasa is discontinued. Guess not. They look like exactly the same product with a different firmware, so I wouldn't be surprised if they had the same failure rate.

After my third KP115 malfunctioned with the classical on-off periodic sequence reported in this thread, I decided to open one and see if these could be repaired.  It turns out that in all three plugs, the culprit was a 470uF 10V capacitor, marked (3) below.  You can see the tell-tale sign of a failed capacitor by its bulge.  I have now replaced this capacitor with a 16V one because I didn't have 10V ones.  It is slightly bigger, but will fit just fine.  To replace this capacitor you need to open the plug up, which is not a straight forward task, since the plug's case is held in place by clips.  I have marked their position with arrows below.  You need to insert a small flat screwdriver under one clip and then prise it open.  Then insert a flat plastic card in the opened gap and make your way to the other clips.  Once you get the case opened, you need to desolder the two mains connectors marked by (1) and (2) below.  Once you free these, you can then remove the PCB so that you may access capactior (3).  Make sure that you take note of the polarity of the capacitor that you remove.  The negative terminal is towards the edge of the PCB.  Once you replace this capacitor, simply resolder back the PCB and click the case back on.  This should solve the problem, at least it did in all three plugs that malfunctioned in my case.   Hope this helps.

I have 10 of them. in the last month i've lost 2 of them. They can't be trusted. 

Oddly the 10 £7 zigbee plugs from china have not failed. 

I thought i could trust the TP-Link ones more but i've lost that trust and will look at replacing them all.

https://www.youtube.com/shorts/hN_3e4Ml3vg

  @vjbutt 

Yep, spot on. Exactly that cap has gone on mine today. Not sure if I have the skill or the inclination to try to fix it...

  @GordonFreeman 

My Tapo plugs are Model P110 and I have 11. The oldest one died a few days ago and was 5 months old. I have recently read that maybe about 1 in 4 P110 plugs will die in a year or two (making a rapid clicking noise). This is rather a worry. I think Tapo needs to recall all of them and replace with a better designed model.

I just had a KP115 fail in the same way, it was connected to a freezer which had ~30W usage most the time with 300W occasional jumps. The switch probably got used twice since purchase (it was bought for tracking energy, not switching). The likelihood is my freezer had probably been getting switched on and off twice a second for a couple of hours before it got caught so there is a chance the compressor has been damaged by this.

On a side note, I have had 2 other KP115s fail where the relay gets stuck on. These were being used to turn a TV off and the max wattage was 60W. Going by the information here, tp-link seems to have cheaped out on the capacitors and relays and as a result the products have been made dangerous.

I am not really sure how to proceed, I have ~15 of these tracking stats through home assistant and its not great if they are not safe to use.

 I've got a third one fail now. Unbelievable, that's half of mine dead. At this rate I wouldn't be surprised at 100% failure rate by the end of the year.

i haven't had time to open them up to look at the capacitors or relay. Contemplating whether it's worth doing that or just trashing these pieces of junk.

Another bites the dust. That's 3 failed the same way now

@everyone I've had a gut full of this in all honestly. I've been dealing with this now for 2 years. I've bought 30 of these devices (KP115's) and so far 15 out of the 30 have died. They've not all died at the same time so I've taken them back to JBHiFi one at a time and got the run around from them each time taking about 30 mins to find the receipts on their systems and done RMAs on all 14 so far.

Today I went to take another one in, that only just failed, to them and they point blank refused to replace it because they said it's now 200 days out of warranty from the receipt they could find. Mind you they didn't take the receipt for receipt so the dates are not the dates on the receipt for the exact device. So who knows which device belongs to which device/receipt any more?

Either way, the device is a dud. In Australia, if a device doesn't perform the way it's supposed to be manufactured it needs to be replaced, refunded or repaired (ACCC law). 

TPLink I say to you how can you let your consumers down and not offer a replacement easily here by letting retails know there's a known fault with these devices and they should be replaced if anyone has one gone faulty on them? It's not simply good enough to just pull them from the shelf and replace them with a new device called Tapo (TP110) and let the consumer fight for their rights. $840 down the drain, why steal from my pocket when you are the ones making faulty devices?