Its normally incompatible bulbs that do this, not suitable for the bulb recognition or can systems.
These are what I put in back in 2012!!! http://www.hids-direct.co.uk/xtec-38mm-c5w-9-smd-canbus-led-number-plate-bulbs-white/Still working fine no errors or nothing!!!
These MK6 OEM ones worked on my 2006 MK5http://www.ebay.co.uk/itm/VW-EOS-GOLF-VII-PASSAT-POLO-SCIROCCO-XL1-NUMBER-PLATE-LED-LAMP-LIGHT-AK-/222272080363?hash=item33c072c9eb:g:8hIAAOSwOyJX9Ttm