Have you had roundup ready on the field in the last 5-10 years? It seems to take a lot of years to get rid of volunteers in any flavour. Canola can be one of the biggest PITA weeds depending on conditions. It especially is a pain when it comes second growth and you want to strait cut something. You can't just desiccate it and use chemicals other than glyphosate to do such. Not allowed.
Had the same thing happen to a research plot back when RR canola was new on the scene. 6 to 8% contamination in non-RR certified seed was documented years ago. Apparently the situation hasn't improved.