A Grapple is performed by:
you try to seize the target by making a grapple check instead of an attack roll: a Strength (Athletics) check contested by the target’s Strength (Athletics) or Dexterity (Acrobatics) check (the target chooses the ability to use).
So, if I gather correctly, a contest is an Athletics check from the Grappler against an Athletics/Acrobatics check from the Grappled. What if the values tie? Who wins?
To free yourself from a Grapple,
A Grappled creature can use its action to escape. To do so, it must succeed on a Strength (Athletics) or Dexterity (Acrobatics) check contested by your Strength (Athletics) check.
In this situation, if the checks tie, who wins?