1999 Ford Explorer Anti-Theft Start problems?

Hi, recently bought a used ford explorer. I'm having trouble starting it, when i put the key into the ignition. I believe it is an anti-theft malfunction, because when i start the car through the remote starter, it works perfectly fine. But when i try to start it through the key itself, the car doors lock up, and nothing else happens.

Is anti-theft causing this? Is there a way i can disable it? Weird thing is, right after i start the car with the remote start, and turn the car off again, i can successfuly put the key into the ignition, and it starts perfectly fine. I'm honestly lost right now. kinda freakin me out lol... please help this is getting pretty annoying . thanks.