Shelly 1 Gen 4, button for gargage door

Hi all,

I installed 2 Shelly 1 gen 4 as button into (2) garage door horman Supramatic. L+N to 230v and I +O to the wall switch which lead to 20-21 at horman board. In the app I used as a button, momentary, 1 sec delay. 1 day latter the Shelly’s blew up and the garage door is not working any more, main board is broken. How could this happen? The device was installed from electrician, what could have gone wrong? Could I have done something wrong in the app to lead the device to burn? And if that happened why was the main board broke ?

I didnt take any photos how it was, and now I removed the shelly to avoid burning the second door main board