Firstly, can anyone verify the story? Secondly, are there any other reports of a similar nature?
From https://trove.nla.gov.au/newspaper/article/148234841:
A cable from Prague states that Bratislava's first experience of a talkie almost ended in a riot. The lack of synchronisation of sound and movement, and occasional mysterious flashes behind the screen excited the suspicion of a film critic, who investigated and found a whole cast behind the screen converting a silent film into a talkie. The flashes were the cue to the muted orchestra. When the public learned of the fake they were enraged and the police had to be summoned to prevent them from wrecking the kinema.
... Hence my question (I split it off from the Nazarine thread).