What could be causing my oven to display an error when touched?
There are two causes that come to mind.  Either you have a build up of static electricity in your body and you are discharging it into the oven, causing the controller to reset, or something in the oven is shorting out to the chasis causing you to get shocked when you touch it.

Do you commonly get static shocks anywhere else in your house?  This is common in northern climates in the winter when everything is really dry.  Often you can improve this by increasing the humidity in your house.

If you do not have static issues elsewhere then it is likely that something is wrong with your oven in the form of a short.  I would advise not to use it any further and have a service person come back and check it more carefuly.  Heating elements failing is a common cause of this.