BUG. A "Detonate" button is not hidden behind the "Unearthed Remnant" window

Before place any bombs. If any "Excavated Remnant" spawn next to the "Detonate" button, the button will not be hidden completely behind "Excavated Remnant" window. Only text of word "Detonate" is hidden.

Expexted result: Button "Detonate" is hidden completly behind "Excavated Remnant". If the cursor hovers over a non-hidden part of the button "Detonate", the button is displayed on top of the "Excavated Remnant" window.