Generally if the handle tension assembly is broken on powering up the Kirby the handle tends to fling backwards as there's no spring tension, If this happens check the locking slot of the handle assembly has not broken off (blue arrow on photo) it could also be that the spring itself inside has snapped, but If this doesn't happen and you have tension I would check the handle stop on the outside of motor casting to see if it has broken as sometimes these do fail (see red arrow on photo) this will generally cause the handle to lean further forward than normal and it's a common fault with these Kirby's. It could be that the two handle lugs (yellow arrows on photo) have opened up allowing for extra movement and they might just need bending closer together.
Regarding your bag drooping down this is common and generally a simple fix, get a large screw driver in between the bag holder lug/clip and open it up a bit wider, If some force has been pressed down on the top bag holder it bends the lug/clip together creating a looser fastening which makes the top bag holder droop down.
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