Here's one with 6: РڠໃמୡඤVŦலڄໃݲథɊІށ௨ಘQɕ௫ҨໃυɷඞМǶ௨ళɱݹ୦Οຯ൫௩ƦഫJமϺຽߢ௧uܘܭЬ௨൧ݹಈඤʆٻҳචHݹಏටฅکҿࡄแחजலາƷ௧οາঐ௧চІͷ௨ౚໃŧԥఠܕɕϢ෯ƚݢƐٮඍԣரಀԀສߜƣƬѣݫΝթֆଔ

I suspect that there's some pathological behavior in the game you can exploit to possibly get a line or more while giving up a line (not that I searched and identified one, I think I just got lucky on my second game because I don't play tetris much so didn't have much of a strategy to unlearn). It would be interesting if there a few of these behaviors that lead into each other, which could lead to a stable state of infinite lines.

Not being random means there might be more to exploit.