Plot hole: Hawkeye calls a number of people into the mess tent over the PA - the ones he allegedly suspects of being behind the thefts he is suspected of himself. Interestingly enough, Ho Jon, later revealed to be the guilty party, is not on Hawkeye's list - yet he shows up uninvited, just to be ensnared by Hawk's clever ploy. Note also that he had no way of knowing what the purpose of the meeting was, so we cannot ascribe to him the motive of wanting to find out how much Hawkeye knew.
Suggested correction: Of course Ho-Jon would come to the tent; it makes perfect sense, since he is the "houseboy" of the Swamp and, consequently, a sort of personal assistant to the Swampmen (Hawkeye, Trapper, and Spearchucker). He simply followed Trapper and Spearchucker to the tent after the announcement, probably figuring they might need him in some way.
It's late evening. It's, as far as anyone knows, an official meeting. Ho Jon isn't "standing attendance", he's sitting at the table (which is very convenient for him to hide his hands later). If he WERE standing attendance, it would be the only time in the series he does so in the mess tent instead of the swamp. It would also be the only time he's attending a meeting anyone called. Also he isn't a "house boy" - that would be totally out of character for Hawkeye, see "The Moose" - he's more an adoptee and roommate who makes himself useful. And last but not least: What a convenient coincidence, that just the guy who turns out to be the culprit would turn up uninvited, because he "might be needed" instead of staying the hell away because he is guilty and suspicious of the whole affair! Had - HAD, which he hasn't - Trapper said "Ho Jon, you better come too", you could call it a Deus Ex, but the way it is, it's just a plot hole, to quote Margaret Houlihan, "period, end of sentence."
Plot hole: Dumb Donald chooses not to play hookey with the rest of the gang. He instead goes to school. The gang is even worried Dumb Donald may, "Rat them out" to the school. Yet throughout the episode, Dumb Donald appears/disappears with the gang as they are skipping school.
The Hold Up - S10-E3
Plot hole: When the robbers come onto the floor and go into Mr. Rumbold's office, the staff suggests calling the police, only to be told by Mr. Harman that the only outside line is in Rumbold's office. This, despite the fact that there have been numerous occasions throughout the series where characters made and received personal calls on the department phones (Mrs. Slocombe calling her cat, Mr. Humphries calling his mother, etc).