At approximately the 49 minute mark, the "duck" plane is in the process of landing, but with no landing gear down. Then all of a sudden when the plane lands on the ground, its landing gear is extended.
At approximately minute 46, one of the Black Sheep's planes are landing and if you look near the end of its right wing you can see several automobiles/motor vehicles driving far off in the distance. The television show is supposed to be on a far off island in the Asian-Pacific during World War II, but you can see motor vehicle traffic that should not be there.
The nurses wear the wrong collar insignia on their green jumpsuits. They are wearing the caduceus with "N" on it which is the symbol of the Army Nursing Corps. The Navy Nursing Corps insignia is a single gold oak leaf.
Buckley flies an English flag from a tree next to his hut. In real life WW II this would've been an excellent way to attract the attention of the Japanese and get executed.
Jeb Stuart Adams (as Jeb Adams) as 2nd Lt. Jeb Pruitt, in several shows of the final season, and Peter Frampton in this one, showed glaring errors respective to Marine grooming standards. Even the Navy did not allow hair that long!! Apparently Hollywood could not let go of "audience appeal" trying to attract teen girls to watch the program. However, this does not actually apply to Peter Frampton, who does not play a Marine but the civilian son of an English planter.
In the shower scene at the beginning, as the nurse shifts position the top of a bikini top can be seen that would obviously not be worn if actually showering.