Weird Lag spikes (with ms not changing) please help!

Ever since the new patch came out I have been having lag spikes. Before you try to run to conclusions here me out because these are not ordinary lag spikes. The thing is the lag spikes re-occur every 5-8 seconds but the ping (MS) remains stable (20ms which is very good and I shouldnt be getting lags). My flatmate has been having the same issue a few days now. We checked our internet connection and its is very good . All other games play perfectly fine. What is the issue here? How can i fix it? has this happened to anyone else?
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