Not much space between swinging arm and frame loop.
On my A10 the left side gap is only about 0.06 inch and right side about 0.2 inch , with bike on stand and rear wheel off ground.
The frame may be slightly distorted after sidecar use, or it may have been dropped on the pillion rest and the loop pushed inwards, or a previous owner has filed a bit off the protruding inner tube of swinging arm bush because they thought it was a tight fit in frame, and put things slightly out of alignment.