Corona SDK Error: physics.start() has not been called

Question

I have my main.lua pointing me to level one, i have an onCollision function which takes me to level two, but when i go to level two, everything loads fine except the physics engine. I get an error in the console saying ERROR: physics.start() has not been called. But at the top of level2.lua i have declared:

local physics = require( "physics" )
physics.start()

This is the end of my level1.lua file:

function scene:hide( event )
    local sceneGroup = self.view
    local phase = event.phase
    if event.phase == "will" then
        -- Called when the scene is on screen and is about to move off screen
        physics.stop()
    elseif phase == "did" then
        -- Called when the scene is now off screen
    end
end
function scene:destroy( event )
    -- Called prior to the removal of scene's "view" (sceneGroup)
    local sceneGroup = self.view
    package.loaded[physics] = nil
    physics = nil
end

The start of my level2.lua is this:

-----------------------------------------------------------------------------------           
--
-- level2.lua
--
---------------------------------------------------------------------------------------

local composer = require( "composer" )
local scene = composer.newScene()

-- include Corona's "physics" library
local physics = require ("physics")
physics.start()

-- forward declarations and other locals
local screenW, screenH, halfW, halfH = display.contentWidth, display.contentHeight,     display.contentWidth*0.5, display.contentHeight*0.5
local centerY, centerX = display.contentCenterY, display.contentCenterX

Why am i getting this error even though i have quite clearly started physics? I've tried copying the exact same code from level1.lua to level2.lua but im still getting the same results.

Answer 1

I had a collision listener in my scene:create function.

    function onCollision( event )
    if(event.object1.myName == "name" and event.object2.myName == "name" ) then
        timer.performWithDelay( 3000, nextLevel, 1 )
        return true
    end
end

I think that this function kept on calling the physics package and returned the error when I progressed to the next level because I had called

physics.stop()

I managed to fix it by removing the event listener in line 4 of the function:

    function onCollision( event )
    if(event.object1.myName == "ball" and event.object2.myName == "finThree" ) then
        timer.performWithDelay( 3000, nextLevel, 1 )
                Runtime:removeEventListener( "collision", onCollision ) -- I remove the eventListener here.
        return true
    end
end

I still get the same error message as before, but the problem seems to be fixed. I know this won't be a fix for everyone, but it worked for me and hopefully it'll work for others suffering the same problem as me.

Thanks to Frozire for helping me.