Complex sentence: The worst problem is that there is a direct current (DC) through a PMOS logic gate when the PUN is active, that is, whenever the output is high, which leads to static power dissipation even when the circuit sits idle.
Split into simpler sentences: The worst problem is that a DC current flows through a PMOS logic gate when the PUN is active, that is whenever the output is high. This leads to static power dissipation even when the circuit sits idle.