As you know I recently got mine on the road and I also discovered a small coolant leak. Took a few tries but finally found it right at the bottom of the coolant "tank", same as yours, polished etc. etc. etc., The hose wasn't really tight so I had added a clamp and thought it would be fine. It wasn't. I had to get a smaller hose for the tank side and adapt it to the larger hose for the radiator side. Spun out a simple adapter on the lathe and seems ok now.
Might be something to check on yours?