I too had a module with issues like this,i began with several layers insulating tape applied to the pcb,which i found less than satisfactory.

Next i applied several layers to the rack frame under the pcb,this i also found haunting,what if the spiky bits penetrate and connect

In the end i found a ready solution from my work which involved the use of printers blanket,this is a tough and long lasting rubber/fabric/adhesive laminate and works flawlessly.

Other issues i have encountered were from another manufacturer where a rotary switch when the module was installed was shorting to the rack frame,this required moving some components of the front of the board and placing them underneath so i could reposition the the switch.

As luck would have it aluminium holes can be enlarged in the direction that is necessary with a craft knife and a skimming action.

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