Fibaro Z-wave power plugs, bad signal

I have three Fibaro power plugs, and I have bad reception from them.

I have nodes 6, 9 and 14. The Zwave controller is in the same room with these nodes.

I believe nodes 9 and 14 try to route through node 6, but I cannot prove that for sure. I have tried to wait for some network heals, but this does not improve my bad signal.

nodes9 and 14 are behind my washing machine and dryer, and this might well be why I see bad reception.

For all three I see:

2017-02-06 19:03:10.477 [hingStatusInfoChangedEvent] - ‘zwave:device:15a09e409ec:node6’ changed from ONLINE to OFFLINE (COMMUNICATION_ERROR): Node is not communicating with controller
2017-02-06 19:03:14.533 [hingStatusInfoChangedEvent] - ‘zwave:device:15a09e409ec:node6’ changed from OFFLINE (COMMUNICATION_ERROR): Node is not communicating with controller to ONLINE

Quite a lot of times (40 or 50 times a day).

Is there some way of improving this, or should I just accept my fate, and move on?

All three have the controller is association group 3 (controller updates), and sometimes I see updates on power usage of the devices, but not very often.