There have been several problems with UEFI on Leap.
As originally installed, it suffered from bug 950569, where some hardware would hang during boot unless secure-boot was disabled. This bug was originally reported for Tumbleweed, but also showed up in Leap. It was recently fixed in Tumbleweed. And today, an update showed up for Leap to fix this bug. The update also fixed a MokManager problem, which I have not personally experienced.
There’s a problem, though. The updated shim package has been installed. But the updated shim.efi was not installed in the EFI boot settings (normally in “/boot/efi/EFI/opensuse”).