My MR 500 was loaded with an EE data only SIM. It started dropping out every evening and would work after rebooting in the morning. Suddenly no data at all. Hard reboot done, still nothing. Checked with tech support, and the data was being sent but not coming through on either Ethernet or Wi-Fi, even though the MR500 showed a full signal on both. Checked the card in the phone, and it was dead. So, get a replacement data card and check it in my phone and all is good. Put in MR500 and the router kills the SIM, no longer works in a phone either. Next,I get a second new SIM and put in a new MR600 and all is good. Stupidly thought that it must have been the SIM at fault and put it in MR500 with the intention of returning the MR600. Big mistake, the router kills yet another card.QUESTION, How is the MR500 killing all new data SIMs and is there anything I can do? many thanks