Linux freezes after a time while running HostAPd

[Conrad Kostecki]

Hi!
In order to create a dual band AP, I've bought two Compex LE900VX cards.
As the mainboard has only one PCIe slot, I also bought a Mikrotik RB14e miniPCIe->PCIe adapter, which can carry up to 4 miniPCIe cards.

Currently, I am running HostAPd 2.6 and Kernel 4.8.4 with newest ath10k-firmware.
Both cards are being detected fine and working.

When I do start HostAPd, the whole server just freezes after a time, usally after 30-120 minutes. Until it freezes, HostAPd is working perfectly fine. When I do not start HostAPd, no freeze occurs and the whole system is running stable.

No errors were logged in dmesg.

Any Ideas, how to debug this?
Are the cards maybe faulty?
Should I ask on the ath10k-mailinglist?

Cheers
Conrad