Chancellor Angela Merkel's government has recently sparred with both France and Britain over the issue, while trouble is also brewing within her uneasy left-right coalition government.
In particular, Berlin's decision to freeze weapons sales to Saudi Arabia over the killing last October of journalist Jamal Khashoggi, as well as the Yemen war, has upset Paris and London because it puts joint defence projects on ice.
British Foreign Secretary Jeremy Hunt voiced “deep concern” that Berlin's stance damaged Europe's defence industry and its “ability to meet its NATO commitments”, in a letter to his German counterpart Heiko Maas reported on by Spiegel Online.
The picture becomes more complex given recent bold future visions to pool European military strengths, partially in response to US President Donald Trump's “America First” approach and his verbal attacks on NATO allies.
As during the refugee crisis, a moralistic political debate within Germany – a country at pains to draw the right lessons from its Nazi and Holocaust past – is now straining the patience of its allies.
Polls have shown that some two thirds of German citizens reject weapons exports.
The centre-left Social Democrats (SPD), Merkel's junior coalition partners, in particular have a strong pacifist legacy and a tendency to condemn corporate profits earned from selling “killing machinery”.
“In Germany public scepticism towards arms exports is almost unanimous,” said Michael Broening of think-tank the Friedrich Ebert Foundation.
“Given its history of belligerence, Germany's public has long viewed arms exports with a mix of moral outrage and helplessness.
“For many Social Democrats the current debate about arms exports seems like a golden opportunity to prove their progressive credentials and sharpen their ideological profile.”
Despite all the agonizing, Germany is among the world's top arms exporters, a club that is led by the United States and also includes Russia, China, France and Britain.
The government regularly meets to review sales under the war weapons control law.
One company that has run afoul of the strict rules was gunmaker Heckler & Koch, which was fined €3.7 million by a German court on Thursday.
Two of its former employees were also given suspended jail terms for illegally exporting thousands of assault rifles to violence-torn Mexican states in breach of the export licence.
Human rights activists had charged that the G36 automatic rifles were used in abuses including the 2014 disappearance — and suspected massacre – of 43 Mexican students.
Last October, when the killing of Khashoggi sparked widespread revulsion, Berlin reacted by suspending arms sales to Riyadh.
Germany urged other countries to do likewise, but French President Emmanuel Macron dismissed the call in unusually sharp language.
“What is the link between arms sales and Mr Khashoggi?” he said, calling it “pure demagoguery to call for a halt”.
'Reduce our influence'
The Saudi issue flared again this week, this time between Germany and Britain, a NATO nuclear power that despite Brexit is set to remain a crucial security partner for the bloc.
Spiegel reported that Hunt had urged Germany to exempt major European defence projects like Eurofighter or Tornado jets, which contain German parts, from its Saudi weapons embargo.
In Berlin on Wednesday, Hunt expressed concern that “changing our commercial relationship with Saudi Arabia… would reduce our influence” in efforts such as helping end the Yemen war.
Maas, an SPD politician, reiterated that the ban remained and said any future decision – a review is due by March 9 — would be “dependent on developments in the Yemen conflict”.
About 10,000 people are estimated to have been killed in the Yemen war since March 2015, but rights groups say the death toll is much higher.
The wider arms export debate impacts large future projects, among them ambitious Franco-German plans to jointly develop the so-called Future Combat Air System of fighter jets and drones by 2040.
Merkel, in a speech last week, signalled a more relaxed stance.
“We have, because of our history, very good reasons to have very strict arms export guidelines,” she said.
But Merkel also stressed that, “without a common culture of defence exports in Europe, the development of joint weapons systems will be endangered.”