The plot thickens... So I finally managed a successful UEFI install (I won't tell you how many chickens I had to sacrifice...) with the latest snapshots (15/09/2015), and following http://blog.jasper.la/openbsd-uefi-bootloader-howto/.
This time I opted to keep it simple and not attempt my usual encrypted install, so I'm not sure whether there was a fix in the latest snapshot or the encryption of the previous attempt was to praise/blame respectively ... I did intend to test an encrypted install with the latest sets, however the randomly booting installer bug is still very much present (see chicken sacrificing...), and after 30+ attempts to boot the usb again, my patience gave out and I'm writing this email instead! Anyone have any ideas why loading the installer kernel is so flaky? It doesn't happen when booting the installed kernels (both the previous, broken, encrypted install, and the current, unencrypted, successful install have no trouble getting past this stage). Anyway I have another picture, as on one of my 50 odd attempts, it threw me a new error message that I hope might be of use to someone... http://i.imgur.com/XOg0AM1.jpg -- 0x2b || !0x2b
