Hi Marius,
There is one but that would only work if you have Shell's access, please give a try upgrading again there is a chance of current boot image getting updated. If it fails again I would recommend you contacting support because there was a change in new R500 I coul not get that right now on my mind which would cause them not to upgrade to older versions, please isolate if that is was we are seeing.
Thank you.
Regards,
Abilash PR.