Help my tablet has reversed its role from being charged to being a powerbank!!!!!

Help me my tablet has lossen its charge last night but then charged it overnight it charged but won't turn on I tried charging it but it wont turn on so i tried many angles and it show a battery icon charging however its the opposite the charger has two cable the other is connected to the other tablet so the chargers light has been turned off and when i removed the charger from the socket its light came back and the other tablet charged i dunno why but it seems that my unknown problem tablet is giving electricity to the charger to the other tablet which is weird and when i put back the charger to the socket the lights goes off and the other tablet won't charged probably cause of the different flow of electricity helpppp!!!! Need an expert!!!!!:(

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