Can't add more than 2 Jobs to Queue

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hey guys,

is this a known bug or am i doing something wrong?
i own keyshot pro for zbrush and i would like to add several camera angles to the queue.
but for some reason after adding 2 jobs keyshot doesn't add any more.
does anyone know what is going on?
(I tried it using the hotkey ctrl-u / using the add job button / add to queue button)

Cheers Chris

Windows 10 - Keyshot 7.1 Pro