This is a Super little lantern but there is a well known problem due to its small size. The wick tube overheads after a short time which causes the flame to grow and flicker badly if not adjusted.
There is a simple solution though. Cut a thin strip of aluminium foil and wind it around the protruding part of the wick tube at the top to increase its thermal mass. This stabilises the flame and it will work well with this modification.
For a more robust result, I added a small piece of brass tube, squashed to shape, to hold the foil in place.