Yes Jean-Pierre!!
You were rigth, there was another issue.
I digged into this problems more and I found that one row in my patchbay was unballanced.
Which became a problem when inserting the EQ531T or the LA502 in the patchbay.
Now I have removed that unballanced row, and inserted a ballanced patchbay instead.
I've had this unballanced patchbayrow for maybe 30 years or so, So I forgott that it sat there.
I allways thougth that my whole patchbay was ballanced, but it was not.
So it became obvious when I inserted the EQ531T or LA502 into the unballanced patchbay.
You always learn something!!!!
Thank you for your patience for my problems.
Regards
Urban Osterman