From my experience, I guess you need a ground plane/net to shield your capsense lines to reduce false detection. If possible add a ground layer in between your capsense traces and other traces.
Details can be found here : http://www.ti.com/lit/an/slaa576a/slaa576a.pdf
I am not an expert on this topic, so I fix my capsense issues from trial and error technique. By the way, is you metal cabinet connected to the circuit ground ? If not, try grounding it and see what happens !
As mentioned by ShHo_1410221, a hatched ground will solve the issue. After connecting the ground hatch, if the CapSense performance is lowered, since Cp will increase, you can connect the hatch to shield and this would improve the performance (emissions might increase though).
You can find more details regarding ground hatch and shield in CapSense design guide.