At a loss for how to dry out safe

I bought this safe two years ago and revived it. I took out the carpet, reassembled the lock mechanism to reliably unlock, removed rust, repainted everything…great. But I cannot seem to remove moisture. I’ve scrubbed it, warmed it, put my basement dehumidifier near it for several days, chucked any desiccant packets I could find in it…but if I keep it sealed for more than a week the humidity climbs to over 70% and everything inside begins to smell musky.