Problem: WFI instruction slowing down SYStick interrupt

I've configured my Infineon relax kit for max frequency(120 MHz). I've set my SYSTick for a periodic interrupt of 10 ms. For power saving, I use a WFI assembler instruction whenever my processor is idle. WFI (wait for interrupt) should put the processor in low power mode until an interrupt occurs. So my processor should wake up after every 10 ms. But somehow, this WFI instruction slowed down my interrupt frequency to almost 3 times and it wakes up on every third interrupt. It wakes up after every 30 ms. What can be possible reason for WFI not waking up on every interrupt?

Regards

Saqib