Split the thick wall vertically so that the reference line of your continuous wall does not intersect the other wall,
OR change the Layer of one of the walls to one with a different
Intersection Group
,
OR change the
Building Material
of the continuous wall to one that has a greater
Intersection Priority
.
If you are using AC23 or 24, you could also use the
Opening Tool
to create your opening.
Ling.
ps. You should add some details to your profile signature regarding your version of AC and the OS you are running as some issues and solutions are version and / or OS specific.