Whenever I try playing League of Legends (a multiplayer game) or be in a Microsoft Teams call, etc. it keeps disconnecting every few seconds, and then reconnects after a few seconds as well, and keeps on like that in a never ending loop. But when I play a different multiplayer game like CSGO, or be in a Zoom call, everything is fine. The internet itself is also working fine, connected and getting my max download/upload speeds.
When I use a VPN (A commercial VPN, like Nord/IPVanish) everything is fixed, but I can't rely on a VPN, primarily because I need to have work meetings on my work laptop that is connected to the company's VPN as well.
I tried contacting my ISP several times, but they keep saying everything is fine on their end.
I tried changing my DNS to Google/Cloudflare and the problem still occurs. I also tried disabling IPV6. I am not behind CGNAT and I have UPnP enabled and working. I also tried turning off my router's firewall.
This problem occurs in multiple computers, different RJ45 cables, etc. So the only culprits in my opinion are either the modem&router or the ISP.
Is there anything I can do to further troubleshoot this problem on my end? My modem&router is SAGEMCOM F@ST3686VB
Thanks in advance.