Well, I will probably screw this up, but as I understand, HeeresGroup D was really another name for OB West, the superior HQ for HrsGp B.
The 136th, while in Antwerp, controlled the 136th (M) regiment, where (M) stands for "Magenkranken", or men who had stomach ailments.
In early September (4th ?) 1944, the British overran the paltry defenses in Antwerp, and pushed out any remaining forces of the 136th that were there. Elements of the 136th Regiment show up in some notes for a while after the 4th.