When I checked your configuration, it seems you're using TCP protocol for Connection Protocols.  Did you try to change it UDP based too?

I've tried it on both to experiment. Basically, sometimes it works and sometimes it doesn't, regardless of the protocol. Either way, on the dashboard Realtime RTT shows 100 (i.e. the reduced value) but in game 80% of the time I get 200+. I've tried on different asian servers but its the same outcome.

Then could you please confirm that it's also same with Full VPN mode enabled?

Okay i tested it out with full vpn and that seems to make 9/10 matches with good connection. However when it doesnt, i get about 350 ping (100 more than normal). However, with full vpn on, i cant browse the web at normal speed e.g. watch youtube videos

Could you please test it again?  Today I'd updated the game item for rainbow six siege.  I'm not sure it's helpful.

Okay been testing it out for a few days now and it is working flawlessly, just like before. Thanks for your help!