Today during preflight I thought the elevator seemed a bit stiff. After a short flight I decided it's actually quite stiff and terminated the flight. Upon instigation I found that the 'horn' between the push tubes (photo below) was so stiff I could hardly move it. Although the plane has been hangared it's been quite warm and humid. I'm guessing the shaft decided to rust. So much so that I was not even able to remove it - yet. The shaft seems frozen in the horn but the shaft moves in the airframe. The bubbles in the photo are penetrating oil.
Has anyone seen this happen before?