I think that is exactly what this is. A hardware issue. More specifically a badly fitting slot or lazy contacts of some sort. There are probably a percentage of units that fit tighter for whatever reason and are not prone to the disconnects. But no way to tell without a couple days of use. I'm not sure how they would fix this aside from maybe a new better slot design.
Look, until we see that new units are immune to this issue, we are exchanging our phones and having to setup from scratch with very little assurance the problem won't still rear it's ugly head by the next day. I'm not sure if it is worth it. I'm not sure what to do. I'm considering just abandoning the idea of the sd card altogether, but I'd be ok with that if I could get a Verizon 64 bit model of the S7E, but alas.....