This time it is Fuchs armored cars produced in Egypt under license that critics allege were used against pro-democracy protesters.
At the same time, the German daily Suddeutsche Zeitung of Munich reported Monday that the country's weapons manufacturers last year notched the highest sales since official record-keeping began in the 1990s.
Approved exports of small arms -- machine guns, automatic rifles and pistols -- and components in 2012 totaled $98.5 million, nearly double that of 2011, the newspaper reported, citing Economy Ministry figures.
These included $8.41 million in exports to Saudi Arabia, encompassing more than half the sales to the Middle East and North Africa in that period.
Criticism of Merkel's center-right coalition has been growing, with leftist politicians and human rights organizations, such as Amnesty International, claiming arms are being sold to unsavory or questionable regimes to suppress dissent and human rights.
Amnesty International activist Mathias John has accused the Berlin government of authorizing the sale of Fahd armored personnel carriers to Egypt that the former regime headed by President Hosni Mubarak used against a popular revolution that drove him from power in February 2011.
John, backed by leftist lawmakers, is demanding the government explain why it's providing arms, or licenses to manufacture German-design systems, to regimes that use them to brutalize their own citizens.
Despite Merkel's drive to boost German military exports, to counter the cutbacks in defense spending be Germany and other European states, German policy still stipulates that arms can only be sold to states that don't use violence against their own people, invade other countries or provide weapons to aggressive regimes.
So far the Economy Ministry has largely stonewalled John's demands for details of arms exports. But in response to parliamentary requests, Berlin has disclosed that in 2004-12 German firms delivered components of the Fahd APC to Egypt where it was built under license.
The Fahd is modeled on the TH-390 APC designed by Thyssen-Henschel, a German defense contractor that was taken over by the giant Rheinmetall of Dusseldorf in 2000.
The deliveries included Daimler diesel engines, chassis and other parts worth $170 million, including shipments valued at $71 million in 2011, the year Mubarak was driven from power.
What's infuriating critics even more, observed the German newsmagazine Der Spiegel, is that of the 1,300 vehicles produced under license in Egypt, "an unknown number landed in countries ravaged by civil war, such as Sudan and the Democratic Republic of Congo.
"Germany's recent actions make it clear that the Arab Spring, which saw citizens in several North African countries rise up against their autocratic rulers, did not trigger a change in thinking about arms export policies," the magazine said.
Merkel insists she's "committed the values" of democracy and human rights but she's come under growing criticism for selling weapons systems to authoritarian states such as Saudi Arabia and the other monarchies in the Persian Gulf, as well as Algeria and further afield to Angola and Indonesia.
"I'm convinced that it's in our interests to enable partners to effectively participate in upholding or re-establishing security and peace in their regions," she declared in September.
Merkel, Der Spiegel noted, "has selected so-called 'strategic partner countries' that she intends to outfit with German-made weapons.
"But there is no requirement that these countries pursue democratic values. Instead, the doctrine emphasizes that they defend Western interests against even more worrying rogue nations."
Under this policy, Germany has expanded arms sales across the Middle East with a $2.5 billion deal to sell the Persian Gulf emirate of Qatar advanced Leopard 2A7+ tanks and 24 PzH 2000 self-propelled howitzers.
The weapons systems are built by Krauss-Maffei Wegmann and Rheinmetall. Berlin's also negotiating to sell 270 Leopards to Saudi Arabia, warships and submarines to Egypt.
The United Arab Emirates, a military heavyweight in the Persian Gulf, has bought German weapons systems worth $1.57 billion.
Algeria's now one of Merkel's "strategic partners" -- "to serve as a buffer against Islamist rebels raging in Mali," says Der Spiegel -- and Rheinmetall's building a factory there to produce 1,200 German Fuchs armored vehicles.