Never actually checked this Z wave stuff

OK, that does make some sense now. You cannot relocate the sensor, so the best you can do is provide repeaters that will insure it gets a decent signal.

It will never get a decent signal as when the doors are closed it's is incased by aluminium. The hub is 15' away line of sight and there are 5 other devices in the same room (3', 6', 7', 12' and 14' away), all capable of repeating. As it happens there is no issue with it if you look at the LWR RSSI (31dB) and RTT Avg (18mS). It reports instantly when I open/close it.