Yes,
I have installed all updates.
Meanwhile, I did the following:
grommunio-virtual-mailbox-alias-maps.cf
...
query = SELECT mainname FROM aliases WHERE aliasname='%s' UNION select destination FROM forwards WHERE username='%s' AND forward_type = 1
...
and bcc_recipients.cf
query = SELECT destination FROM forwards WHERE username='%s' AND forward_type = 0
and in main.cf:
recipient_bcc_maps = mysql:/etc/postfix/bcc_recipients.cf
And then both forwarding modes work.