some of the files you can just umm, 'mess up', by accidentally hitting something on key board when you're not actually attempting to edit then saving with other changes

I've managed that in character traits before (couldn't find and had to completely re-do), the data/text ones are susceptible if you do anything to first character in file by mistake. Haven't met it in EDU or DMB but it is possibility from your description.

If you start again do it in small stages, eg adding 5/6 units max at a time, and keep backups of each previous stage, its easy to get lazy on that once you think you know what you are doing but it is a lot safer!