Talk:Mods 2.0/@comment-96.243.239.172-20130513224004/@comment-123.27.38.69-20130520114936

1. There aren't any difference between mods which come with the warframe and mods that drop, except that you can't use the mods come with warframe to fuse for another mod.

2. Basically, you will still receive ALL four mods that come with the warframe even if you have all those mods in your inventory at the highest level.

So I believe that your case is just a rare bug. I've built 2 warframe so far and I receive all of their original mods even though i have most of them in my inventory already.