Coyote Time Not Functioning Properly

So, I've coded in this simple code to implement coyote time. However, I've been getting this bug which causes my player to double jump, I've been trying to fix it for the last few hours and I still have no clue what to do.

Code (CSharp):

1.         if(Input.GetKeyDown(_inputManager.jumpKey)){
2.             _jumpBufferValue = _jumpBuffer;
3.         }
4.         if(_jumpBufferValue > 0 && _coyoteTimeValue > 0){
5.             _jumpBufferValue = 0f;
6.             _coyoteTimeValue = 0f;
7.             Jump();
8.         }
9. //////////////////////////////////
10.         if(_isGrounded){
11.             _coyoteTimeValue = _coyoteTime;
12.         }
13.         if(!_isGrounded){
14.             _jumpBufferValue -= Time.deltaTime;
15.             _coyoteTimeValue -= Time.deltaTime;
16.         }

I've tried setting the coyote time to 0 but it is still not working, anyway thanks!

 

The Isgrounded and !isgrounded are in the fixedupdate function while the ones that detect input are in the update function.