Dirty or Damaged Rollers – These help the window glide smoothly. If they’re stuck, the window jams.

Misalignment – Over time, the frame may shift or warp, preventing a proper seal.

Debris in the Tracks – Dirt, leaves, or insects can block the sliding path.

Bent Frames – Can occur after impact or long-term pressure.

Weather Stripping Failure – Missing or damaged seals can let in air even when the window appears closed.