Slow fps doubling movement

When the fps is really slow, the jump height and speed are roughly double than if the framerate is normal. The movement I use uses rigidbody2d addforce to apply movement. Any way I can solve this issue?

By any chance are you using Time.deltaTime in LateUpdate()? If so, try using Time.lateDeltaTime instead.

Move your movement code to FixedUpdate() instead of Update()