[ghaff]

Especially once everything was spliced onto one big reel, no not common. But when you were switching from one projector to the other every 15 minutes, there were more things to mess up and it could happen from time to time. More common was just a botched reel change of some sort in which the old reel ran out and the timing to switch to the new one was off for some reason or there was just a problem with the film threading.

[hedgehog_irl]

Only time I had it happen in 7 years was when due to failing bulbs not striking so easy I had to strike em manually and left the manual switch in the on position. Well there was a power brown out and that killed the basic automation on the machines that would close a dowser when the film stopped. So the film stopped but the dowser stayed open and the bulb burned through. And for good measure that exact same thing happened on 2 machines at the same time. I believe I was heard in a screen as I responded to the situation with something like "For F*k sake" while restarting the other screens before having to splice the 2 burned films.

To clarify these machines were platter fed so no changing reels. The dowser was used to light the bulb while the leader was still running through but not to be on-screen.

Edited for typo and to add more details

[ghaff]

On the projectors I used I think doing the dowser thing was manual although the switchover was somewhat automated otherwise.