Question lagging in online games

[Cauliflower88]

Having an issue where I am lagging in my online games, but I have already talked with two technicians saying that my modem is working great, there is no packet loss and the connections to the modem are great. I am using a PC with ethernet. Is there a third party program where I can test what is actually going wrong within my online games? Also not sure what can be the problem if it isn't the modem. I get the download speed and upload speed that I am supposed to get, reaching 170 down 35 up so I don't think that could be the problem. Hopefully somebody can help me out. Thanks

 

[rgd1101]

full system spec?

what game having issue?

 

[Cauliflower88]

Processor: i7 9700f | GPU: 2060 Super | RAM: 16GB 3200MHz Corsair Vengeance RGB | Storage: Intel 660p | Case: Phanteks Eclipse p400s | Water Cooling: NZXT Kraken x72
I'm having issues in Rocket League, can't really tell if it's in other games since this is the main game I play.