TTP223 touch sensors self-triggering bug

I have three TTP223 touch sensors connected to a power source (only VCC and GND are connected).

I intentionally didn’t connect I/O pin to Arduino because I suspected that it could cause the problem (trigger the sensor by accidentally sending current to the I/O pin). One of the sensors gets triggered and starts blinking, please see the video:

https://www.dropbox.com/s/y0eeg959fybol … 5.MOV?dl=0

I fail to reproduce this bug consistently and don’t know what causes it. I’ve noticed the following:

  1. It happens only on the 1st and/or the 2nd sensor only if they are both connected (but after switching sensors and then assembling this same setup - sometimes this bug disappeared).

  2. Thought they were too close together and were triggering each other but I tried putting other sensors even closer and it didn’t happen.

I would be very grateful for any ideas on why this is happening, thanks in advance!