Z-Wave Switch module keeps dropping out of network

I have a Fibaro FGS223 in the summerhouse at the bottom of the garden to control the pond lighting and the summerhouse lights.

Thinking it might be a bit of an ask to include it in the network from there (probably over 35m from the hub) I installed another FGS223 at the bottom of our Garage steps (About 7m from the hub) Then an Everspring relay half-way down the garden to control the back gate light (Around 15m from the garage steps) Each of those meshes reliably with the system and are happily part of the smarttings system.

I paired the Summerhouse 223 switch well within range of the hub (as per the Fibaro instructions, then installed it at the bottom of the garden, at which point it was working fine. But later that day it had dropped off the network altogether. The only way to get it to appear is to remove power from it altogether (Luckily it’s on a fused switch) and then turn on the power again, at which point it becomes available. I have no real idea what to do next. Any ideas?

So I have tried using the Z-Wave Repair utility and I get two messages in the log:

2018-06-15 11:37:28.793 AM BST | HUB | zwNwkRepair | failure | Network repair for Summerhouse Dual Switch [07]: Failed to update route
2018-06-15 11:37:53.396 AM BST | HUB | zwNwkRepair | failure | Network repair for Summerhouse Dual Switch [07]: Failed to update route

Is there any way to see the non-failure logging messages for the Z-Wave repair utility?