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Barbarian3D has got this one, I concur. The bed isn't flat. as suggested try the glass bed, I've had the same issue and the glass bed completely fixed it on one of my Ender 3's.
If the problem still persists (& if it does it will be much reduced) try putting a 3inch square of standard printer paper in the middle of the bed under the glass to raise the centre slightly.
The bed is slightly warped with a dip in the middle. I personally don't use and auto bed levelling on any of my Ender 3's.