It is true, it is not even necessary to move the red block. Just leave it still while keeping a space so that the blue block can be inserted.
I think this happens because the blue block detects that the route is blocked (the red block blocks the route when you press the right cursor), then the blue block looks for the exit on the left.
But this should not happen if there is enough space for the blue block to be in the area.
That is, the area is large enough to keep the blue block there, so there is no need to look for an exit on the left.
This error seems to only occur towards the left side.