leonardo built board disappear

hi there!
i m having a weird bug since a few days, very time i upload a sketch, everything runs fine.
but when i want to reupload a sketch, the IDE can t connect to the board.
that means everytime i need to upload a sketch, i have to restart the panda.
that makes it a pain for iterations/debug.
i ve read a few forums threads about that bug. but nothing seems to fix it.
and i haven t found a proper leonardo driver to force neither.
any helps appreciated !
thanks in advance !