Unfreezing rotation causes the position and rotation go crazy

I am currently making a game in which exact location and rotation are very important. So I want my Player to land exactly on 0,0.75,0 whenever the level starts:

however, whenever the player (blue cube) lands, the position and rotation change by a bit, which is a game breaker for me. I know that those are small numbers, but still, this IS a game breaker.

I tried to fix this with this piece of code, but it works only for the first second, and during that second I can't rotate the cube, which is also a game breaker:

 IEnumerator OnCollisionEnter(Collision col)
     {
         if(col.gameObject.name == "Surface")
         {
             yield return new WaitForSeconds(1);
             rb.freezeRotation = false;
         }

BTW, I'm pretty new to unity (and doesn't know JavaScript at all), so please consider that when helping. Thanks for everyone who will!! :)