@Pj000001 

Thank you for your detailed post.

Do you mean  two PC monitors are plugged into the two Tapo P110, and the monitors power Off and ON? 

Can you help describe how the monitor power on and off in details,  do you mean monitor lose power and get power immediately? 

- Please connect your Monitor to a wall power socket and test performance

- Only connect one PC Monitor to Tapo smart plug and see if issue persists

- Test a different Tapo P110

- What the model of PC monitor and its wattage? 

If Smart Plug itself turn OFF and On randomly:

try to check if you have set up Shortcut/ Automation settings 

Turn off other third party apps that might have a chance of affecting smart device behavior

If  this occurs again, try factory reset  tapo smart plug, in factory default state (Wi-Fi Led flash amber and green), does it still turn on/ off or reboot?
 

 Hello  @Pj000001 

Thank you for detailed information,  it does not seem to be an issue with smart plug but more likely something relates to the ' middle' device between tapo plug and the monitor. 

Smart Plug is a relay to cut power and provide power to all connected devices. In your case, only certain Devices like PC monitor powers off, but other device gets power. 

From your description, you have smart plug --- --USB hub ----PC monitors,  i'd recommend to check if USB hub could provide enough power to the connected devices. 

Hope this helps.