I wouldn't know if TTP223 is made to act differently, but if you touch a length of plain wire to the inputs of a logic gate, or op amp, or mosfet or bjt...
It becomes an antenna picking up 60 cycle hum. The output produces a 60 Hz square wave.
Sometimes this happens even if nothing touches the input terminal.
And if you touch your finger to the bare wire, and you carry a static charge, it causes the output to go sharply positive or negative (depending on whether you're positively or negatively charged).
It may continue this way for several seconds while the static discharges from your body. Then the output drifts back to an oscillating waveform.
These phenomena are on-again off-again, sometimes unpredictable. Sort of like the problem you report. And your inputs have a length of bare wire attached.