Random z-wave behavior

I have just installed a Homey together with 6 Telldus Mini Plug-in switches. But I have some issues that makes the entire setup wothless.

After some trial and error I figured out that the switches had to be 'centimeters" from the controller for the pairing to work.

But when everything finally was paired and placed I cannot get the switches to work consistenly.

For example, when I run a flow to turn on the six switches it sometimes works, but mostly one or two random switches never toggle.

My setup has max 3-5 meter between Homey and/or another switch.

Does z-wave on the Homey work this badly or is it just me doing something wrong? I would say that this random behavior makes everything quite worthless.

Note: I have tried both the latest and latest experimental firmwares with the same results.

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