I'd be looking for condensation on the West side of the big lens.
If you have any spare BBCs, I'd be trying those. 103W is stacked with 110W and 119W while 99W and 101W are stacked together.
Stack Plan (from WB68 manual)
Ka-Lo, 99° RHCP
Ku, 101° RHCP
Ka-Hi, 99° RHCP
Ka-Lo, 99° LHCP
Ku, 101° LHCP
Ka-Hi, 99° LHCP
Ka-Lo, 103° RHCP
Ku, 119° RHCP
Ka-Hi, 103° RHCP
Ka-Lo, 103° LHCP
Ku, 110°/119° LHCP
Ka-Hi, 103° LHCP