How to stop Safari randomly closing tabs when I try to restore it using Cmd+Shift+T?

[Shirasaki]

I've been driven crazy by Safari for quite a while recently, and now it decides to close the tab I want to restore randomly!
Specifically, I open a couple of tabs, close them for whatever reason, and then want to reopen them again without going through the process of finding them. Cmd+Shift+T right? Nope. Safari will randomly decide the tab I want to reopen does not want to be reopened and close the reopened tab automatically immediately after pressing the hotkey.
How can I permanently disable this nonsensical behaviour and use Safari in one piece?

 

[kitKAC]

I've always used CMD + Z to undo the last closed tab but I just tried CMD + SHIFT + T and that works for me without closing the tab I just reopened.