Battery sensor fail after falling

Hey everyone, I got an iPhone that fell flat on the back (didn't got any physical damage on the outside) after this, the battery indicator shows only 1% on battery, restart every 2-3 min and the system no longer recognize the battery (never changed the battery and before this I could see the battery condition at 85%). Opened the device to check if something is damaged inside, however, it is as good as new, so disconnected the battery (both connectors), blow some clean air and tried again and the problem was no longer happening and no restarts, charged normally and can access the battery condition. Then I put every plate back on, and to my surprise, the problem reappeared when I turn the phone back on. Doing some tests (trial and error) notice that the problem only happens if I secure the bottom plate. In this case, which part should I replace? the battery? that board that connects at the bottom of the battery? would change only that part, make the battery unrecognizable by the system as if I changed the battery?. Also, was doing some research about it and some people mention about a failure of the battery sensor, where it is located? (based on the fact that the bottom connector is the one failing I suppose, that is the location). Thanks for your help in advance.