Rear Admiral Chegwidden states that Yeoman Second Class (YN2) Coates' promotion to Yeoman First Class (YN1) would be effective 1 May. This would not be the case as enlisted promotions are effective the 16th of the month; officer ranks are effective on the first. More accurately, Petty Officer Coates' proper effective promotion date would be 16 May vice 1 May.
When Mac and John seek to catch a train, the sound of a steam whistle aboard a steam locomotive blows repeatedly. Amtrak has never operated a steam locomotive. In the USA the last one went out of regular passenger service during the 1950s. All Amtrak locomotives have always been diesel or electric, not steam, and they use air horns, not steam whistles.
If Mac and John had truly boarded a train to start a train journey from Washington, DC, to Colorado, they would have done so indoor at the Union Station in downtown Washington; however, they do so here at a dark outdoor rural platform.
In the scene where Mac and Harm are going through their things, right after Mac tells Harm that "loving you is like stepping on a rusty nail", she heads into the bedroom. The pink mukluks that she's wearing are certainly not uniform issue. This may be due to an ankle injury suffered by Catherine Bell, as in the next scene, Mac IS wearing uniform issue pumps, but her left ankle is wrapped.