@Naagod 

1. In Google Home, delete the association with all Kasa devices.
2. Make sure all the Kasa devices have unique names.
3. Then go back & establish the association with Google Home. 

@DeanGibson already done that, doesn't do the trick. but thanks!

@Naagod How close are plug2 & plug3 to each other?

1 in a bedroom the other in the bathroom so 7 m2 apart, connected in the same wifi. The plug 3 is also in the same bathroom next to the plug2, but never had a problem. 

Right now, as of this post, both plug 1 and plug 2 are controlling plug 2. Names are different (camera and dehumidifier), but I simplified For the purpose of this thread.

@Naagod Hi, as a small update on this, after months of trying I decided a new approach. I disconnected the TP-Link service from my Google Account and created a new Google Account which then I connected to the TP LInk devices/account. It was ok for a few tries, but it still doesnt work. How come anyone else isn't having this problem? This is beyond me.

I guess I'm switching from TP- Link do something that doesnt have this problem or switch from Google to Alexa.

@Naagod I am having the same issue with Google Home. I have 4 HS103 plugs and 2 HS210 switches. All switches and plugs work properly within the Kasa app but there is a device conflict within Google home. One smartplug in particular turns on a different device in Google home instead of the lamp It is plugged into. I have tried removing TP-Link Kasa from Google and re-adding, syncing devices, removing and re-adding within the Kasa app and nothing seems to fix the issue.

@steve_dcalz yes, that's my problem here (thank god I'm not the only one). Already talked with google a few months ago, their answer: 

If it's integration issues I'm afraid I really can't do much.You can send a feedback via voice command so that this will be directed to our Product and Engineering team. Just say "Hey Google, Send Feedback" you'll be given 90 seconds to state your concern, in the Feedback just mentioned that you are experiencing integration issues with your Google Nest Mini and TP Link smart plugs.

I was able to overcome this by creating a new home, and putting the Google Home Mini associated to Home1, and the TP-Link devices associated to Home2, and then control all devices from the same Google Mini. But this suddenly changed from the last Google update I guess, because now (unlike before), it is not possible for a Google Home device to control devices in other Homes.

This is such a simple problem that for me, as a developer myself, would keep me up at night if I were in either Google or TpLink teams.

@Naagod What's curious about this to me, is that I have 31 Kasa devices in my home, & three Google Nest Minis, & I have never seen this.

I assume you have the various Kasa devices grouped into rooms in Google Home, although I can't imagine how that would make a difference.

Two suggestions:

1. Buy an Amazon Echo Dot, & see if that works any better (I have two, & they coexist nicely with Google products).  That will allow you to isolate the problem between Google & Kasa.
2. Create "Routines" in Google Home & use those to turn on/off each plug. A work-around to be sure, but it will stop you from going crazy on this.

Note that Google software is not what it used to be, in terms of QC.

@DeanGibson Hi yeah I have an Alexa and has no problems like this. This is so random that I cannot even describe a possible reason for this. Sometimes if I open the Kasa app first and reload the devices, when I go to Google Home App and interact on the devices it will work. Other times after I refresh the devices on the Google Home app it also works. Other times it doesn't. As a developer, I've actually done a battery of tests covering different use cases, and nothing adds up. For whatever reason this might be, there's simply no excuse to mix between two devices unless their ID or name is the same.

I can't create routines as in my country that doesn't work. Another reason to switch to Alexa.