(at around 21 mins) This episode reuses a nighttime exterior shot of a German airbase from Some of Their Planes Are Missing (1967). However, the Heroes are supposed to be at an armaments factory, not an airbase with airplanes visible beyond the gate and fence.
The 'Kurt' that discusses the plans in the barracks with Hogan is not the same 'Kurt' that appears in the Hofbrau to take Fraulein Muller away. These are two different actors. In addition, the one in the barracks has a mustache, and the one in the Hofbrau does not.
After Schultz is ordered by Kurt to report all his activities to his commanding officer, he goes to Hogan and asks him for support when he meets with Klink. After Schultz leaves the barracks, Hogan takes off his robe, opens his pajama shirt, and opens the tunnel entrance. At that point, Hogan says, "All right, wait 'til you're in position. You know what to do." Those two sentences appear to have been dubbed. The only sound other than Hogan's voice is the sound of the bed lifting to open the tunnel (which is probably a standard sound effect anyway). Before and after those two sentences, there is considerable background sound of the men moving around, but not during those two sentences.
The German-language paper Carter is reading is a then-recent issue of the "Los Angeles Freies Presse" (a German-language Los Angeles-area paper), from Friday, April 22, 1966.
When Carter, Newkirk and Kinchloe approach the new factory at night, there is a very brief clip (two seconds) of what seems to be "re-used" footage of the fenced and guarded RAF fighters that was shown in a very recent episode.
The grenades that the men throw over the fence are not strong enough to trigger something that would blow up the factory. In addition, the factory buildings should not be in range of someone tossing a grenade from the other side of the fence.
(at around 2 mins) Sgt. Carter says, "Hey, what are you doing with my mattress?" But his mouth is not moving.
After bringing Kurt up into the barracks, the men leave the tunnel entrance open. The entrance should be closed, as someone may come in and see it.
When Carter, Newkirk, and Kinchloe throw their grenades, they are so close to the fence that they have to throw them almost straight up. Since the trajectory is parabolic, the grenades would have fallen only a few feet inside the fence - which could have been fatal. The men should have been back several feet in order to throw the grenades at the optimal trajectory to maximize the distance they would travel.