How to fix current leaking and zapping


I have OnStep smt32 bluepill kit. Other day I powered it off using my smart switch. I accidentally touched my mount and got zapped. I found out that my Smart switch cuts only one wire, depending how is it turned, in this case it opened N so L was in circuit. I thought my power adapter was faulty so I ordered new, stabilized, quite more expensive one, but I got zapped again. So i used multimeter and mesured 55V on the mount. I guess that is due to capacitor in power suply adapter. 

So if it was AC i would use 1:1 isolating transformer, or I would ground mount.
 I cannot ground mount easily, and I did found some DC to DC 1:1 fransformers but it is said that is not a good option. What is? I know it is not dangeorus current, but I prefer none. 
Did anyone else had similar issues? 

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