I wasn't using this wifi adapter in the meantime, but took it out again few days ago. Now that the kernel is updated to: 4.1.31-30-default #1 SMP PREEMPT there is this additional line in dmesg output when the problem happens: ieee80211 phy0: rt2x00usb_watchdog_tx_dma: Warning - TX queue 0 DMA timed out, invoke forced forced reset