Just one example: I am hearing far too often that France is overly protecting their own interests and as such can't reach important deals with Germany about sharing burdens and profits. So it results in duplicated, incompatible systems. Germany is generally more open to share benefits and intel with other countries.
Such deal-making can drag on for decades, to only fall out. For industries to scale, they need long term planning and a guaranteed pipeline of orders. I am talking about ships, planes, MBT's, air defence, missile tech--not riffles.
It is a shame, because both countries are powerhouses in engineering. Also, this costs EU taxpayers billions of dollars, and perhaps their safety even.