Maybe the local studio didn’t get the first reels of the film and they aired what they’d advertised in the tv schedule. Or someone misloaded the film out of sequence.
I’ve heard that Ernie Anderson/Ghoulardi would pack too much non-movie content into some of their late night broadcasts some weeks that he’d show the ends of the films next time or even bundled up a number of the ending (this was Cleveland in the 1960s).
In the 1980s in Boston I saw a channel (55 or 56, it’s been decades) that would show cartoons (like Loony Tunes or Tom & Jerry) that had been trimmed, they were putting in more ads and to make up for it, they’d trim one 7 minute cartoon down to about 4 minutes by removing the first 3 minutes after the opening title. They’d also just omit the end credits from movies from the 1970s and 80s. I don’t recall if they did that with tv reruns as well.
Oh yeah I noticed the same thing as a kid. I also noticed that by the 1980s the networks were trimming movies for more commercials. I especially remember GOLDFINGER in the 1980s was trimmed of the first scenes, opening instead with the Miami scene and not the scuba and explosions or the “shocking!” scene.
As for OHMSS, the network purposely started in the middle, then reverted to the first scenes for some reason I never understood.
A FIST FULL OF DOLLARS, when shown on network TV had a fake five minute introduction of the man with no name getting government instructions to investigate the border towns, that was not in the movie. They even gave it a dialog to lip sinc mismatch to make it look “Italian”.