yesterday i updated my octatrack to get those nice trig conditions. update went thru and the new feature is there. but i cannot load any previous project. always a wrong checksum?? and all my sets are gone except one. all samples from the other sets are lost. when looking at the card there is only that one set and the projectfolders with no audio files.
i know there is no solution i just need to vent a bit 
I’m really sorry for that. did you backup your projects on your computer?
sadly not. i should have done, but frankly i use the octatrack because i hate computers somewhat…
anyways, time for an new start 
so i’ll delete every other things on my a4 + aR as well
This is an incredible zen solution. 
You may want to take a look at OctaZip which makes the process of backing up stuff as painless as possible. Actually, OT is the most approachable of the Elektrons in that respect.
Yeah, I’m staggered in admiration!
Sorry to hear, but that’s a good attitude to have.
I try to back my card up from time to time, because I’ll occasionally get a bad checksum when I load a project (using a Sandisk Extreme 64gb). Between occasional backups and always saving at least two versions of any important projects I’ve never lost anything of value yet (only had two projects get corrupted so far, and the first one may have been a case of not waiting long enough after the card light stopped flashing before powering down - I like to give it a few extra seconds just to be on the safe side).
Backing up is really just a matter of copying all of your files over, unless you have so much on there that it takes up a lot of space. Octazip is pretty affordable though, so might be worth a try when it’s OS 1.3 compatible (I bet it would work fro 1.3 machines already since the file structure is the same, but it isn’t officially supported yet). I haven’t used it but it sounds good.
Alternatively, there are some free differential backup programs, you could just use those if you don’t need to backup or migrate inividual projects and just want to maintain a current backup of your whole OT card.
Could it be possible for you to reinstall v1.25 in case that version can read the files from the CF card? I don’t know, but I suggest that you contact Elektron support to let them know of your problem, in case others suffer the same issue.
thanks for your input. octazip looks quite interesting. thanks for pointing this out.
I would try the OS rollback @PeterHanes suggested, before deleting all your work, if you haven’t already. 
At any rate, before you start trying stuff, try to make a backup of the card.
I also saw wrong checksum error one day…
Since then I duplicate my main project every week by using “save as new project” and then copy whole CF content to my computer via usb. 
Snugglybunhead had some vaguely similar sounding issues and had to move around some stuff to get it working:
I’d hook the OT up to a computer and fully examine the card.
-Did your set get moved into a folder somehow?
-Is there no Audio folder with your samples anywhere?
@Open_Mike I have the same problem. I updated from 1.25h to 1.30a first, then b and then 1.30c a couple of months ago. I’m getting the checksum error when I power on and the OT loads the current project in memory. Not every time though. When loading a project made in 1.25h for the first on 1.30c it works fine. Then I switch of the OT, and the next time I turn it on and it loads everything it reads checksum error and asks if I want to abort loading. I choose No, and then “save the project as new”. Then it works again with everything intact. What should I be looking for when checking the CF with a computer? What files should be where? I have all samples for each project in their own Audio folder, not an universal Audio folder for all projects.
Edit: I’m using a OT MK1
The issue I was bringing up was slightly different, she had to move folders around to get things working…
It sounds like you just need to save the projects created in earlier OS’s again so that they are saved under the new OS…
I generally do that first thing after an update, load old project, save project, reload project…
Don’t know if that’s necessary but it makes me feel better and I haven’t experienced issues, I’m stil on 1.25H though…
Alright! Error messages are always a bit scary. But then I will not worry any further.
I haven’t upgraded yet and have never experienced error or wrong checksum, keep an eye on it and post if anything happens. Other nauts might have more on this if it’s happened to them…
Nothing wrong with 1.30B for me…for the moment.
I’m not in a hurry to install 1.30.C
1.30.E maybe ?