[BUG] Generating with CONTENT, it get the content double

[Regna91]

If I use CONTENT-Object for rendering like this

lib.register = CONTENT
lib.register {
    table = tt_content
    select.pidInList = 21
    select.orderBy = sorting
}

I get the content twice on the page.

temporary solution:

If I use RECORDS-Object with uid of the gridelement, then works

lib.register = RECORDS
lib.register {
    source = 25
    tables = tt_content
    dontCheckPid = 1
}