I'm late to the party on my acquisition of a Shuriken, and have recently experienced the exact same issue. I ran the test in Workbench that was suggested above and was able to confirm fairly strong bleed-through of the detuned E string after reducing the A string volume to 0%. Additionally, if I reduce the E and D strings to 0%, I can then palm mute the A string without issue.
Based on those tests, it would seem that the issue is conclusively "un-fixable" in the current iteration of the instrument, but I thought I'd check here to see if anything has changed in the last few years - or if anyone has developed a reasonable work-around.
Thanks!