I don't know what too do or what it can be I'm lost...
This won't cure your problem but may give you some insight, while the battery is up, disconnect your negative (-) clamp and see if it sparks when touching the post. If you have a draw, it will spark. Then the fun starts in seeing what it is. Sometimes it can be the security system.
2002 Black GT (Spectre)
2011 Red Candy Metallic V6 (Manfred)
2016 Magnetic Metallic GT (MkIV)