Client Lags. Can't pick champ. Leaver buster

So this bug keeps happening and I haven't seen it addressed yet. In my client during champ select, the client will randomly lag. So although we are picking champions, my client will still be on the declaring champion stage. Occasionally it will quickly catch up (zoom through banning, and the picks) but more often than not when this happens I cant pick a champion and it times out, I have to close out the client and I get penalized for leaving champion select. i can still chat normally with players while this is going on. Is this a known bug or is there something I can do to fix this? I have already uninstalled and reinstalled the game so unsure if doing that again will have any affect. historically my computer never had an issue with the client. Any help is appreciated.