At home, I run a pair of SXTsq 5 ac devices to span my network to a place where I can't be bothered to run a cable to just yet. After installing a VoIP phone in that location, I noticed reoccurring periods of time (about 17 seconds each, maybe varying from 15-20 seconds) where packet loss was high. This was made clear by choppy audio on phone calls.
After further debugging, these drops were occurring almost 5 minutes apart, down to the second. I initially thought this was some external interference source, but that was not the case (confirmed with another device and the frequency-monitor tool built-in to RouterOS). It turns out that RouterOS wireless clients will automatically scan for APs with better signal when they are connected to an 802.11 wireless network. This process can cause disconnections and periods of high latency.
You can disable this behavior with
/interface wireless set station-roaming=disabled [interface].