Be sure to check out the Guru3d news article for more details but there may be issues with firmware updates 3B6QCXP7 and 3B7QCXE7. It is worth checking your firmware if you have weird intermittent issues. Link below.
Guru3d breaks the news on a 4TB 850evo model!!! Check the source link for the full read. Personally none of my reseller channels have it even listed (just the enterprise version). Currently the highest capacity SSD a customer has used is the 850evo 2TB....who is in for a 4TB version? :)