Where to Find Encrypted Charr Battle Plans

Hi all, this is my first post here, so bear with me.

So I had some Encrypted Charr Battle Plans, and decoded them and got the missions. But then of course I failed the missions and since I had turned in the plans, I don't have the missions again. The question is, where do I find the plans again?

I believe I found them the first time in the Warband of Brothers Mission, do I have to do that mission over? Or would any of the storyline missions do? And before you ask, I already searched the wiki and this site's forums for this information and didn't find anything. If I missed something, please let me know!

Thanks ahead of time for your help!

Kill charr, get plans.

Any charr in EotN.

Afaik they're a random EotN charr drop.

I'm relatively sure that they only drop from the high level Charr, ie the ones that aren't from Prophecies.

Doing the Ebon Vanguard primaries are the fastest way to get these.

The drop rate for these seems to be ridiculously low. I've done the Vanguard primary quests with three characters, all the secondary quests with two of them so far, all the dungeons with one of them, and cleared Grothmar, Dalada, and Sacnoth a couple of times to boot. After all that, I got exactly one set of battle plans. One. (And, unfortunately, failed the mission.) This is one sick mechanic to get access to missions, if you ask me. At the very least you should be able to repeat any one for which you've obtained the plans.

I only ever got one. And that was during the EotN preview weekend.
Never seen another since..

Thanks for the help. I suppose I'll try redoing some of the Vanguard primaries and see what happens.

I've seen three, two for the same mission. I found all three in probably a one month window while doing EV quests, and haven't spent a lot of time killing Charr since. I have stacks of Map pieces, but not very many battle plans.

Almost every single time i go into Rragar's Menagerie I get one of the battle plans to drop at some point in the dungeon.