I had a problem with a Schneider unit similar to what you're experiencing, see this thread:viewtopic.php?p=5026
I suspected either RF interference or that our AC line, with a 6.2kw solar array grid-tied, might be to blame. We now have a Clipper Creek EVSE, and there have been a couple times it has stopped, but generally speaking it is working for us now.
Incidentally, I also had an EVSE Upgrade unit for maybe a month or two in that time, and it too would stop charging (though not like our original Schneider unit did).
Do you have solar or some possible RF nearby as interference? It could also be the car needs a software update; some situations may have been out of specification originally (higher voltage or GF leakage) may have been dialed back because of these problems (and understanding of no additional risks in doing so). I have no idea what goes into the software updates, so this could be way off base, but maybe you should take it to the dealer and see. Or try your EVSE at the dealer, see if they can reproduce the problem there.
Just some thoughts.