Vogels projector bracket help (EP6565)

Hi all, need some help from anyone with the same or similar PJ mounting bracket... I can't get the pj off the bracket. As per the instructions you unlock the disk and it should release... Mine isn't... Embarrassing as I mounted it initially on the bracket 3yrs ago.
Below an image of the disk to be unlocked by rotating clockwise.
Need to get the pj for a damage report tmrw so any assistance appreciated

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