as far as i know its a comon problem with the m4 aqua, for some reason all anteannas are problematic (this includes wifi and bluetooth).[br]
A workable solution is to put preassure on the NFC logo on the back (this also fixes bootloops that a probably caused by the anteannas too).[br]
I have a case for my M4 where i put a piece of rubber right at the NFC logo, so it gets constatnly pressed and that seems to work and fixes most of the problems