It seems to check whether the current frame is >= to endframe before it goes to the inframe which, obviously, is not whats required
the reason it stops and doesnt start in your example -
at the end of CUE 2 - the current frame is 600.
the next cue ( CUE 1 ) has inframe 1 outframe 301.

as this is playing forwards in ONCE mode - the possible next possible inframe/outframe must be larger than current frame - it isnt. so nothing happens.

this is correct behaviour.
playforward DOES NOT Retrigger - and you have programmed a cue that has a inframe/outframe range that would stop the cue anyway ( if the current frame was anywhere after the outframe of cue 1 ) ...without an explicit goto frame command.

( lighting consoles have no notion of 'current frame' - if they did - then maybe just maybe it might be possible to do something a bit cleverer )

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you need to be more explicit in the behaviour you require by programming an additional cue with either inframe or an intensity change and use the retrigger playmode.

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i could add an extra playmode which explicitly retriggered when the inframe or outframe values were changed.