I have a EX5601-T1 router and I am experiencing "micro-disconnects" when connected via wifi

Furball

Hi,
I have a EX5601-T1 router and I am experiencing "micro-disconnects" when connected via wifi.
The "micro-disconnects" is noticeable when playing an online game (game freezes every 20 seconds or so for less than a second which causes a "stutter" effect in the game) or when watching a streaming video like Netflix (quality drops or the video-player starts buffering, happens every few minutes).
When doing speed tests everything looks great the speed is good (over 300Mbits), the signal looks strong so there is nothing that can explain the weird behavior.
Any ideas how I can troubleshoot this problem ?