Quick questions: have you checked that you are able to save ship designs yet? and do you have full control of the Saved ships folder? (Try Following what Walt suggested I should try above if you haven't yet)
--Also does saving Ship Designs work at all when Avast has all shields turned off?
Ex:
Disable for 10 minutes run the game and save a random ship design (Make sure to turn Avast Back on! after you save a ship design)
So I have paid off the internet mafia and got a "digital signature" for Cosmoteer. Theoretically this makes both Windows and anti-virus programs more trusting of Cosmoteer. I'm curious whether it fixes it so that you can save ships without having to disable your anti-virus/ransomware.
You'll have to re-download 0.12.7 and re-install to get the new digital signatures.
Walt After looking around some more with Avast it actually has a list of items it will attempt to protect from any changes done to it by unallowed apps.
(As an experiment I turned of picture files and it will now allow any programs to alter pictures, same goes for Cosmoteer, makes sense, as your ship design files are pictures)
You can still allow cosmoteer following the steps I provided above. (once I did that I didn't have to disable any of the shields from Avast)
(Although I did redownload to see if it can work without 'Allowing' your program, sadly I guess it's still a different matter so it didn't work without being allowed)
--In order to fix this, your program has to be more trusted by Avast themselves I guess. since it does say:
(don't really know if you can fix this but good luck! and continue making some good progress!)
I cnt open the game, it runs at 30 fps then crashes on the loading screen. How ould i fix? im 13 so i dont know jck, but i dont have any mods installed....
Martzocalypse Please start a new thread and post the error.
Walt As an alternative option, can you please make the save files folder configurable?
(as a quick fix, add it to the rules.txt)
That way we can put it in a folder that our virus scanners is not hellbent on protecting.
(I can not get AVG to ignore my "My Documents"-folder)
Boosterdraft_nl You can do that via a command-line option. For example: --rootsavepath "C:\CosmoteerSaves"
Walt I use AVG can you explain on how to do that fix?
Jonathongun Create a shortcut to Cosmoteer on your desktop (if you don't already have one) and then follow these instructions: https://www.lifewire.com/command-line-parameters-video-games-3399930
Walt I have tried that and I am still having the same problem I have tried all of your previous steps and still nothing
Jonathongun Then unfortunately the only advice I can give you is to turn off any anti-virus or anti-ransomware programs you are running.
Walt I will try that thank you for all the help 
Figured out for AVG users, since for no aparrent reason my Cosmoteer started doing the access deined Nonsense since the only recent thing i have done was update the AVG and when i worked on any ships or tried to make new ones i got
so i read alittle of all the previous posts and found that if you go into settings, Full Protection.
Going to Ransomware Protection.
then press the View allowed/Blocked Apps button
then select the allow app and locate Cosmoteer.exe should solve your problem and works for other games that might have a similar Issue. hope this helps anyone who has AVG cuz it is Frustrating when AVG interferes with programs that work.
Jonathongun i found the solution for sorting it for AVG, see my post above
