Intermittent Connection Drops. Please help.

Hello, apologies for writing in English, my Dutch is not yet on the level to to discuss technical topics. 

On Friday, 18 August at about 18:00 my internet connection went out for about ~15m, restarting the Box 12 did not help. It seemed to resolve itself out, but what I have started noticing are random brief disconnects. 

I went ahead to plot ping graphs to one.one.one.one(1.1.1.1) Cloudflare DNS, that is also configured in the router in “Thuisnetwerk → DHCP”. 

What I saw was what seems to be random connection drops but with each drop having the same duration of about 3 seconds, in most cases.

Over a span of 30m I had about 5% packet loss. Attached are screenshots of ping plotter.

The modem displays that the internet connection is being active for 0 minutes each time this happens, meaning that the router lost it. 

I work remotely for a High-Frequency Trading (HFT) firm, where network stability is incredibly crucial to my job, as I need persistent connection to remote hosts, and these drops time me out of my remote sessions. 

I would appreciate any support.

Router model: SagemcomFast5359_KPN

FW version: V12.C.23.04.33