Comment # 14 on bug 1207900 from Takashi Iwai

/etc/zypp/zypp.conf should be with simply a few more entries like:
  multiversion.kernels = latest,latest-1,latest-2,latest-3,running
It's for allowing to install more kernel packages than default (= 2).

Then just download kernel-default.rpm from the OBS download URL, e.g.
 
http://download.opensuse.org/repositories/home:/tiwai:/kernel:/6.0/standard/x86_64/

And install it directly with zypper install --oldpackage option, e.g.
 % zypper in --oldpackage kernel-default-6.0.12-1.1.ga6c4f4e.x86_64.rpm

Boot with that kernel and retest.  If the test is done and the kernel is no
longer needed, uninstall it
 % zypper rm kernel-default-6.0.12-1.1.ga6c4f4e