The belt is not required to be extremely tight. As a matter of fact, it just needs to be taught. A belt that is too tight will increase the amount of torque required for the motors to move the head.

Skipping teeth would likely not be an issue (especially if the belt is set to the correct tension). It comes down to the fact that the motors can't spin because they can not output enough torque. A belt that is too tight may exhibit this behavior.

Is there any information you can reference for the belt tension of your specific printer?