Hi, I've asked this question on a few other forums with little success so hoping someone here can help. A year or so ago I built myself a speaker enclosure from MDF. I glued and screwed the joints, the joints were filled with U-POL P38 filler. After the glue was set I removed the screws, drilled out and filled with dowels. Everything was sanded down and then I sealed the MDF with watered down wood glue. The finish I was after was a high gloss black, I'm no expert just a DIYer but I was pretty happy with the finish. Anyway to my question, about 5/6 months after painting the joints began to appear, these had sunk, and where the dowels had been placed, these began to looked raised. Below are a couple of pictures which show my issue. I'm now thinking of making a new box but I don't want to make the same mistakes. Instead of using screws then replacing with dowels I can use internal batters to construct the box but my main concern is regarding the join lines that appear. One one of the forum's I posted they said it was caused by the vibrations in the box but I'm not convinced by that, the box is totally sealed. Another and seems to be the consensus that the mdf holds moisture and can shrink/expand, another forum suggested that after sealing to use wood hardner. Surely everyone's builds are not suffering this so what would be the suggested approach to stop/minimise this? Any advice would be welcome. Thanks, Marv.