Throughout the movie, the 2nd Reconnaisance Battalion appears to only consist of two platoons of soldiers. A Marine Corps or Army battalion normally consists of companies, which, in turn, consist of platoons.
During the rifle range scene, Jones shows up with a steel pot helmet in an attempt to tease Gunny Highway for being old. He is admonished and told to remove it and wear the standard issue Kevlar helmet instead. Since the film takes place in 1983, the steel pot helmet was the standard issue at the time, so Jones' wear of it would've been proper. Kevlar was not the standard issue helmet for Marines until 1985-86 (when the movie was filmed).
In the morning scene in which all the men wear the same black t-shirt as Highway, when "right face" is ordered, Swede performs the facing by kind of slinging his right leg around, rather than pivoting on his heel. No man or woman who'd been in any U.S. military organization longer than about 36 hours would perform that action incorrectly. It's obvious that the actors were not instructed properly.
When Highway encounters re-con platoon for the first time ("No speaka English" and "No habla") he pushes the hut door open with his left hand but in the next shot, from inside the hut, it's his right hand pushing the door open.
The final scene was supposed to be located at MCAS Cherry Point, home of Marine Air Refueler Transport Squadron 252 (VMGR-252). However, the insignia on the hangar is that of the VMGR-352 Raiders, revealing this scene to have been filmed at MCAS El Toro, California.
Midway into the film Stitch Jones is surprised to learn that Gunny Highway is a Medal of Honor recipient. Yet up to this point Jones has had ample opportunity to observe the decoration on Highway's uniform. As the nation's HIGHEST military decoration it is placed on the left breast, first and highest above all others. Equally hard for any of the recon members to miss would be the sight of Highway's superiors (like Maj Powers) being obliged to initiate the salute to the lesser ranking Highway - a privilege, by tradition, extended to MoH recipients.
In the beginning of the film, when Highway stands to attention as the colors are being lowered at sunset, the bugle call being played is "Taps". However, the correct call is "Retreat". Taps is played later in the evening at Lights Out.
While scrambling around the barracks before the Emergency Deployment Readiness Exercise, Jones mentions Aponte "getting his big cartoon face back here before he does time for doing 'A-W-O-L'". The Marine Corps does not use the term "AWOL". The Navy and Marine Corps analogue for AWOL is actually UA (Unauthorized Absence).
When Highway and Recon platoon conduct their live-fire operations in Grenada, none of the Marines are wearing either protective headgear ("Steel pots" or Kevlars) or body armor, which is highly unlikely.
In several instances, the unit to which GySgt Highway is assigned is referred to as "Recon Platoon". If the unit is, indeed, 2d Reconnaissance Battalion as is assumed, there would be no "Recon Platoon". The entire battalion is "Recon". It is possible that the actual goof is in his assignment to 2d Reconnaissance Battalion. With the way the movie is written, it would make more sense for him to be assigned to the reconnaissance platoon of a Marine Corps infantry battalion, hence the rivalry with the apparently conventional 1st Platoon.
While chastising GySgt Highway on his altering of the ambush plan, Maj Powers mentions that the men belong to the 2d Marine Division, 8th Marine Regiment. 2d Reconnaissance Battalion has never been a subordinate unit of 8th Marine Regiment. This supports the notion that perhaps the goof is in Highway's assignment to 2d Reconnaissance Battalion.
When GySgt Highway gets on the bus at the beginning of the movie and takes off his Class A suit coat he is wearing a Class C short sleeve shirt. This should have been a long sleeve shirt and tie per Marine Corps uniform regulations.
Just before the mission into Grenada, the fully-camouflaged Lieutenant Ring is wearing a shiny silver bar on each collar point. This is never done in combat, because reflective metal makes the wearer easy to spot. In 1983, a USMC First Lieutenant would wear a black bar on each BDU collar point.
After 'Swede' Johanson gets up from his altercation with Sgt Highway, he says, "Sir, I'll wait outside for the MPs." As both are enlisted men, Highway would not be addressed as "Sir". Such formalities are reserved for officers with the only exception being Drill Instructors when being addressed by recruits. Swede would have addressed him by rank or "gunny".
Gunny Highway's Recon Platoon is commanded by a 2nd Lieutenant (LT Ring), which is the right level of command for a platoon in the Army or Marine Corps. However, 1st Platoon appears to be led by Major Powers throughout the movie vice a 1st/2nd LT. Army and Marine majors command at the battalion or company level, never at the platoon level. Another 2LT/1LT should have been in charge of 1st Platoon.
When the unit returns home and they have the parade and marching band, the drummer of the band has the 1st Marine Division emblem on his drum. If they were in Cherry Point, it should be the 2nd Marine Division emblem.
When the platoon is briefed at the start of the Grenada assault, they are told they are to recon ahead of the main assault; however, the assault is clearly underway and troops are ashore well before the platoon has been dropped.
When Highway is in a bar near the beginning of the movie, he watches a performance of "the Ayatollah of Rock & Rollah". However the "Ayatollah", whose singing is amplified, doesn't appear to have a microphone.
At the beginning, when Gunny is in the prison in 1983, it's possible to see a calendar indicating Saturday 20th and Sunday 21st July 1983, but actually 20th July 1983 was Wednesday and 21st July was Thursday.