QDEC high power consumption

Hello. Project im developing requires low power wireless encoder. NRF52832 is a really impressive chip that handles everything i need within 40uA. But I've got problem with QDEC. I just can't get it running with current consumption less than 400uA. SDK QDEC example also consumes 400uA, but datasheet specifies current of 5uA. As I can see, there is 3 possible options:

1) I'm making something wrong and there is a way to run QDEC with high efficiency

2) Forget about QDEC and process data in RTC IRQ - possible data losses due to softdevice IRQs

3) Connect RTC to QDEC START task using PPI and short SAMPLERDY event to STOP task

I have no idea about reason why current consumption is so high. Time between samples is 128 * 2^SAMPLEPER us -  so maybe QDEC uses PCLK1M? But I found no information about clock source of QDEC. It would be nice if there would be some undeclared/reserved register that could solve the problem. Probably someone should have thought about connecting QDEC to LF clock. 

However, it's all just a bunch of random guesses. I have no information about detailed QDEC architecture and just hoping for best