ASRock Z170 Extreme4 UEFI freeze

I have an ASRock Z170 Extreme4 motherboard  with 1.6 bios.
I've been experiencing occasional freezes while navigating UEFI menus. The mouse cursor still moves, but the interface stops responding. Sometimes it recovers after a while but most of the times it requires a hard reset. 
It's not a critical problem, but it can be very annoying. 
Does anyone know what might be the cause, and how to solve it? 

The rest of the system is composed of an i7 6700k, with 2*8GB of RAM from G.skill and an hd5770 from powercolor, with an OCZ arc100 as boot drive. 

Thanks in advance. 

Just thought I'd add I've been experiencing the same with 1.80

I'm having the same random freezing issue with Z170 Extreme6 board. It has happened about 3 times by now. Both with shipping bios version (can't remember what number exactly) and with latest 1.5.

I also have issues with BIOS freezing randomly. Z170 Extreme6, BIOS version 1.60 (latest). Sent an e-mail 2 days ago through ASRock web form, I have yet to hear back from them.

The issues also extend to BIOS becoming inaccesible because pressing Del will instantly reset the system instead of entering BIOS. Also, the keyboard randomly doesn't work in BIOS. Very dissapointing product. I will decide next week if I will return the board or keep it because the thought of going through the process of dissasembling the PC again, return the MB, order a new MB, wait for it to arrive is too much for the little time that I have.

They don't need to respond to individual e-mails but what they could do is put an announcement for the Z170 series products page with big bold red letters stating that they are aware of the BIOS issues and they are working on them.

It's quite hard to trust them when they don't even communicate with us. I also saw many complaints and RMA's on newegg. They actually did respond there, to each individual review/complaint.

I am a first-time user of an ASRock MB and I was initially wary of them because of their (past?) ties to ASUS which I will never touch again on the MB side since a few years back when I had 2 boards from different generations fail on me completely (they were mid to upper tier, Deluxe class). And now I get this headache when finally deciding to upgrade to Skylake after 8 years (from a Q6600).

I just wanted a solid board that won't fail on me with normal usage (I have I7-6700, not K, not interested in OC-ing). I have little time on my hands to play around with an unstable product.

Fortunately, the system works well when not trying to do stuff in BIOS but given these issues I wonder what other surprises my ASRock MB has in store for me. I will have to do some extensive system-wide benchmarks and see if there are other potential issues derived from the still beta stage BIOS.