It seems support for the emonSD-26Oct17 was (accidentally?) dropped in a recent commit
I’ve submitted PR’s for this version to be reintroduced but even once those fixes are in place, you won’t be able to pull them in as support for your image has been temporally removed so the update won’t run to pull in the fixes.
A work around is to edit the version file to a supported version so the update will run and then change it back so as not to cause any further confusion caused by reporting the wrong base image.
If you ssh in and run the following from the command line
rpi-rw
sudo mv /boot/emonSD-26Oct17 /boot/emonSD-13Jun18
you should then be able to update as usual and then after ALL the updates are done (ie update now and then again when the fix to the versions is merged by @glyn.hudson )
rpi-rw
sudo mv /boot/emonSD-13Jun18 /boot/emonSD-26Oct17
you could then try running the update again just to be sure all is hunky-dory.
As for your original “processing” issue, I’m afraid I haven’t a clue, but it’s worth asking, have you tried clearing the browser cache? (ctrl-f5)