Believe it or not, but the problem is solved by replacing the lsu....
As explained earlier in this thread, Sharp advised us to first replace the lsu, and so we did...
I suppose that it had something to do with a faulty yellow laser beam, but it's strange that there wasn't any fault code.
So because there was no exposure to the yellow drum, the whole surface was continue charged.
Unless i see it wrong....
So thanks anyway!!
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