Just had another plug failure on a plug feeding my NVR. Same clicking failure mode ant this is now 3 out of 5 units failed. Obviously a design flaw and totally unacceptable that these products are still being sold! 

  @Lethalas  beware using cheap capacitors,  these are obviously stressed components. I didn't have 470u but had some 100u solid electrolyte automobile grade. High ripple current and will not dry out. 

That's fine if you are happy to use a device which can potentaily fail without warning, rapidly switch the mains supply to your devices on and off when it does. If your devices can cope with that then great. I won't take that sort of risk powering far more expensive critcal eqipment though and would rather swap them out for something that fails safe. 30 bucks is a small price to pay to protect severs worth a grand or more. 

  @UnhappySteve 

I too am losing faith in these devices. I am using them now just for Christmas lighting, those lights flash on and off anyway so a failure wont harm them but for critical stuff like my HASS server, my Office Server and my Pond system, I am replacing them. I just cannot risk using something that can fail and take down expensive equipment in the process.

  @cbc001 I have also had the same failures on 2 out of 5 of my Kasa KP105 smart plugs. I changed the failed units out with Tapo P100's but after reading this forum I am concerned that the Tapo's have the same design flaw. 4 of my 5 plugs are used to supply critical smart home infrastructure so I am very concerned with the failure mode of these devices causing expensive component damage to my equipment. TP-Link refused to replace one of my devices when it was just 3 days past its warranty period so I am very unhappy with the TP-Link brand and have totally lost trust in them. I think my safe bet is to bite the bullet and throw all my Kasa/Tapo smart plugs in the bin. Thinking of replacing them with Meross smart plugs as I have had good experience with the Meross devices I have used thus far.

Can anyone confirm that the Tapo smart plugs have the same design flaw and failure rate as the Kasa plugs?

I found that at least one of my plugs was running warm and heat was accumulating around the area of the cap. That can cause failure over time so I opened the device and drilled some small 2.5mm ventilation holes in the base of the cover and in the area around the cap on the top of the cover. This should help to keep it cool and the cooler electrolytics operate, the longer they last.

Interestingly, several others that are not plugged in vertically but horizontally instead show no signs of getting warm at all. having them plugged in 90 degrees anticlockwise from upright seems to help.

Another one done. 5 lost now

  @thewatcher  so far had only one of 6 fail with just this problem. As noted by some one earlier it is a capacitor failing on the dc low voltage power supply  of the plug circuit. I have opened up all the kp115 and kp105s I have to check this capacitor out - only the faulty one was showing the bulge on top and this was beginning to eject the aluminium case from the capacitor!

It is indeed a flaw in either design or manufacturing. The capacitor is being stressed and either it is too cheap or incorrectly specified for its operation.

To open the UK version I have found that the bottom case junction (nearest the live/neutral pins) of the unit has only one tab locking it in place. A knife inserted into this  and twisted can make the front cover bulge and click out from its lock. careful use of a thin blade screw driver and the knife can then be moved round the case un-clipping it from its location (2 down each long side and 2 on the top. NOTE THAT IF ANY OF THE TABS OR SLOTS GET DAMAGED THE THE CASE MAY NOT SECURELY LOCATE WHEN REPLACED. glue may be used to prevent safety problems. 

If there is a capacitor failure it can be replace ensuring polarity is correct. the original cap can be removed without un-soldering by pushing hard and rocking the case back forwards until it breaks the leads. A new cap can then be soldered to the pads  on the circuit board. Note that this will not give good shock resistance!

There seems to be 3+ different version of this circuit. I have changed this cap in only 2 of them. ! seems a very different circuit.

DO NOT ATTEMPT ANY OF THIS UNLESS YOU KNOW WHAT YOU ARE DOING!!!! 240V IS PRESENT ON ALL PARTS OF THE CIRCUIT INCLUDING THE LOW VOLTAGE SIDE

As people have said this failure could be disastrous - some things should not be continuously power cycled and for example heaters could be powered momentarily (50% of the time?) when not expected. It is dangerous that tp-link have not recalled these.

three types of unit kp115/105