If you do have another Pi (or remove this one from it’s case) you could try connecting a screen and keyboard. although the desktop isn’t installed in the emonSD, you should be able to see how far (if at all) the emonpi is getting before failing. The printout to screen might give you the info to fix it eg running a disk repair utility.
If you have another SD card you could try putting another copy of the emonSD image in the emonPi to see if that boots. If it does, then you could plug in the card reader and old image to inspect/fix/back up.
Are you referring to the age of the SDcard or the vintage of emonSD image?
Unfortunately the latest image is not read-only, therefore the chance of failure during a power outage is significantly higher. That was a big benefit of a read-only OS.
The reason cards corrupt when power is removed is usually due to a incomplete write, ie the power was removed mid-write and the data corrupted. With the pre-oct18 images, the writes were limited, the fs was read-only and only when the feedwriter saved data from memory, momentarily every 60s, and when config files were edited etc, was the system vulnerable to power off corruption, now the OS is not RO, the writing is less controlled, it could be writing at any time, it’s a game of chance. IMO you’d be quite unlucky to corrupt the SDcard this way since the logfiles are still in RAM, but none the less, that risk has increased with losing the RO FS. I use simple battery backup UPS’s on any SD based device that isn’t RO.