now advancing and now retreating; ebb and flow; seesawing; taking alternately favorable and unfavorable turns
交渉は一進一退を繰り返している。
The negotiations keep going back and forth.
病状が一進一退で家族は不安だった。
The patient's condition seesawed, worrying the family.
一進一退の攻防が試合終了まで続いた。
The back-and-forth battle continued until the end of the game.