Network latency spikes every 20 seconds

On my LG G3 running Android 5.0 I have a problem that I started to notice while playing Clash Royale (a real time multiplayer game). My actions would sometimes have a delay of up to 2 seconds. Other players wouldn't have that problem. So I started investigating. Here are the facts: - I'm always on my home Wi-Fi. - When I ping my router from my G3 I can see a spike in the latency exactly every 20 seconds. - It is not location dependent, reception is good. - Other devices don't experience this using the same Wi-Fi. Hence I think this must really have to do with my G3. It is not rooted and I haven't been playing with any internal settings. Displaying the CPU usage from the developer settings doesn't show anything suspicious during the spikes. Has anybody experienced anything similar? Any ideas how to further track down the root of this issue?