I used to have a lot of packet loss and lag spikes when playing in the evening or even at noon (during summer when school is out) in multiple games not just val, tried a bunch of things from forums and yt, but nothing worked. Ended up contacting my provider and described my issues they said it could be bcuz my connection was on a IPv6 which is newer(and as the specialist told me, because it is newer the game servers are not properly optimized for it) and so they switched it to IPv4 and since I've had no similar issues. That said idk if this is what causes your issues but you could try looking into it