Regarding the apparent SIM issue, and having reported that I could reproduce putting pressure on TOH, where the SIM is, to disconnect it, and to demonstrate other use cases: I've just jumped about 40 times with the phone in my jean's front pocket and no disconnection happened. Don't ask why I jumped, maybe it was only to make this point, maybe not ;-)

TL;DR: my SIM disconnection problem may not be _that_ serious, or at least device/SIM dependent.