I'm not going to go into a lot of detail here unless asked, but they need to be fixed for characters who linked accounts. For example, amass 5 swords in your inventory. I'm looking at 5 of them right now. Also the get an item to heat level 10. I dunno what else is broken with the achievements, but it should be looked into.
http://steamcommunity.com/id/ksib/screenshot/541772047562925046
Quiva is correct. The achievements work properly, but are not retroactive in some instances. I believe this was stated when they came out, but I am not 100% on that fact.
I understand stuff like... you have to have crafted x amount of items and it not registering as the server may not actually track how much stuff you crafted; but to have the swords IN your current inventory for the achievement I mentioned simply doesn't make sense. Something tells me if I bought one more sword it would probably register, but I shouldn't have to do that. That's not working properly.
Any achievement that isn't counting something that you've done and the server can check is broken. I don't know how anyone could argue against that.
Anything that the server can't check for, obviously, you'll have to do again like how much mineral you've deposited or how many times you've revived yourself and others, and so on.
Hopefully this gets a patch too, but it looks like they might have more on their plate looking at the bug posts.
Actually, to get the achievement you must make a whole new line of equipment after the implementation of the achievement system. So, if you have four swords and the achievement calls for five you will need to make five new ones and not one more. I can verify this, as I have obtained every crafting-specific achievement. That is, unless, this has been patched. I know that I took my time getting the helmet achievement and it was still the same.
Often, when implementing something like achievements, actions only count towards the achievement AFTER that system is implemented. I have over 20 crafted items in each category and, to date, have only the first one or two steps in the crafting achievements since I had those items before the system was put in place. So it's not a bug, really, just what happens when you implement a system like this after the game has started.