display problem with GMEDIA

hi,
i have an issue with the display screen of the GMEDIA gallery creation.
when i try to create a new gallery, the screen turns transparent grey and the column with actions buttons doesn’t appear correctly (on the left side, truncated) so i can’t creat anything.
this problem even arrive when i try to install module (always in the same plugin)
I send a message to the support of the GMEDIA plugin but without any answer yet.
it’s seems to be a wordpress display issue, so if anyone can help me to fix it or tell me why it’s appear.
thanks

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