Some users of the Echo II triggers report issues with light strikes on the primer, however that has more to do with the buffer weight than with the brace or any buffer tube or stock you may be using.
I had a few light strikes using this brace and the echo. From what I was able to find out is that this can be fixed by replacing the carbine buffer with an H1 buffer and has nothing to to with the brace or any other or buffer tube/stock you may be using. I have not tested since I installed the H1 buffer.
I used this brace on an AR pistol equipped with the Echo AR2 trigger. It worked fine except for two light primer strikes which could have been me over-running the trigger or could be attributed to breaking in a new pistol upper. The brace continues to work just fine with the Echo. No other issues aside from those two light strikes so far.
I have this brace on a 10.5” 5.56mm pistol with an Echo ARII. I really enjoy it. I have experienced one or two light primer strikes, but it was still during the pistol’s break-in period. Other than those light strikes, it’s run flawlessly. The brace is fantastic and is surprisingly comfortable. Very easy to install and operate.
I have a couple of Echo II triggers in a SBR and a pistol with this brace and have no problems. I believe if your gun works fine to begin with it will work fine with the brace.... and I shoot mil-spec 55gr or 62 gr green tip to insure proper functioning.
I do have this very combination in my pistol and I can tell you that with an H1 buffer I have not had a single issue after 1000 rounds.