Repeater Dissapear When On The Up Placed A Block

I Had This Bug When Building A Door That Use Command Block
Sorry For No Screenshot
I Place A Repeater And The Up i Place Grass block When I Test My Door Using command Block
It Wont Work i checked All Work Then I Press The Button One Repeater Wasnt Working But Its Connected Then I Just Put A Block Then Its Placecable I Break It It Repeater Gone I Didnt Break The Repeater