I'm having the same problem but here is what I was able to find.
Download and install this [https://play.google.com/store/apps/details?id=net.vinagre.android.emmc_check&feature=nav_result#?t=W251bGwsMSwxLDMsIm5ldC52aW5hZ3JlLmFuZHJvaWQuZW1tY19jaGVjayJd|EMMC] and [https://play.google.com/store/apps/details?id=jp.nomunomu.dummy&feature=search_result#?t=W251bGwsMSwxLDEsImpwLm5vbXVub211LmR1bW15Il0.|Dummy file generator]
If the EMMC gives you insane ship then you are one of the unlucky people like me. Try then the dummy file application, some people reported it helped.
To be honest, I feel it's a temporarily solution. It seems that Samsung doesn't use Good quality components. I've tried stock ROM and everything out so far the alliance-rom.com is the best stable one with me. After the installation you might try to install the Perseus kernal. Mine is better than before.
Good luck,
Zak