Small but really BAD mistake in this film

First, I say I like/love (somewhere in between) these Strachey movies! The gay part and the mystery/adventure of it. But I am NOT exactly a fan of Ron Oliver's film directing. Aside from that, to the point, I just noticed something watching this again... at the end, where, outside the building, Don shows Tim that he found Tim's sister... when Time goes and talks to here, Don and Kenny are talking in front of the door... there's a shot of just Don and Kenny talking, and behind them, a guy walks out of the bldg. behind them,... big guy, yellow sweater, jacket, black knit cap, ...just a few shots or cuts later, Kenny and Don are still at the door, but in a shot with Tim and his sister in the foreground and Kenny and Don in the background, the SAME GUY in the SAME OUTFIT walks OUT of the DOOR AGAIN!!!! Geeez, fire whoever was responsible for continuity or extras!!!